Bitcoin Forum

Evening all, this will be my first post on the bitcointalk forums. 8)

I've been around for a while, reading through guides and keeping track of everything enough to build myself a rig with the following specs (from Newegg):

• 1 x Antec One Hundred Black ATX Mid Tower Computer Case
• 1 x SAPPHIRE PURE Black P67 LGA 1155 Intel P67 SATA 6Gb/s USB 3.0 ATX Intel Motherboard
• 1 x Intel Core i3-2105 Sandy Bridge 3.1GHz LGA 1155 65W Dual-Core Desktop Processor BX80623I32105
• 1 x Crucial Ballistix Tracer 2GB (2 x 1GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory w/ Green LEDs Model BL2KIT12864TG1608
• 1 x MSI R6990-4PD4GD5 Radeon HD 6990 4GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card with Eyefinity
• 3 x SAPPHIRE 100311SR Radeon HD 6970 2GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card with Eyefinity
• 1 x SILVERSTONE ST1500 1500W ATX 12V 2.3 & EPS 12V SLI Ready 80 PLUS SILVER Certified Active PFC Power Supply
• 4 x COOLER MASTER SickleFlow 120 R4-L2R-20AR-R1 120mm Silent operation Red LED case fan

I kinda went all-out on building this one, ended up costing ~2700USD. I also built this back when the price of bitcoins were much higher.. I had expectations of making it big. Those were the days, eh?~

Anyway, so I've finally gotten all of this set up with Ubuntu 11.04, such that I plug the system into the wall (directly), power it up, after 5 seconds or so it boots into Ubuntu from an internal SSD, its set up to automatically connect to the wireless network in my house, and it runs VNC and Hamachi on boot for me to remotely access it. I plan to eventually have it automatically overclock and start mining on boot after 20 or so seconds.

IT ALL SEEMS TO WORK FINE, except for when it comes time to actually mine. 2 of the 6970's I've left with the stock BIOS voltages, one I have overvolted in BIOS to 1225mV, up from 1175mV stock, and I've left the 6990's alone BIOS wise. The BIOS switches on all the cards are set to the 'enthusiast' warranty-killing mode. I set all the core clocks of the cards to 900MHz (seems like a safe overclock, up from 880MHz stock), and that one special 6970 -- which is special because I've stress tested it enough to know that it can run @ 1000MHz for at least 6 hours straight under full load without hitting 83C -- I set to 990, just to be safe.

Mining runs for a few minutes with phoenix, and after a few minutes the system crashes. Flat-out sudden shutdown. Fans stop spinning, the works. I look through the case, and the LED's that light up to indicate that the PC is on are still on. I hold the power button for 7 seconds to shut them (and the system?) off. I try to power it back up -- nothing. Just like before, the power-on LED's are active, but I'm assuming the PSU isn't providing the juice since its status light is red.

So here's the thing. I'm wondering if I have a defective PSU. 1500W should be enough to power 3x 6970's and 1x 6990, right? I've underclocked the memory on all the cards to 180MHz (the lowest I can go before I notice a performance hit in MH/s), and the CPU is obviously a low-tier model which is not overclocked, and I haven't overclocked the system RAM, so I'm not sure where to point the finger here. This 1500W supply is supposed to be REALLY GOOD. It has a great rating on Newegg, it's very efficient, and its 1500W. I can't imagine that I'm exceeding the wattage requirements with these cards mining. Or am I?

I really wanted to post this in the Hardware forums, but since I'm restricted, here I am. Halp. :(

Well the one way to make sure if it's the power supply or not would be to take a few of the video cards away and test to see if it makes a difference.  If lowering the amount of cards in operation at once provides the same results, you should test each card individually.  Doing so would rule out having a defective card.

If the PSU can truly handle it and none of the cards are defective, the next thing you should look for is either CPU or GPU overheating.

Other than that I have no idea what to tell you.  Usually the only thing that would take a system down is a major misconfiguration or hardware issue.  Given what you've said, the only thing that makes sense is either defective hardware or overheating.

Well, and to clarify: after 20 or so minutes, I can boot the system back up again, so it's *very* likely to be an overheating issue. Just not sure where.

You don't even need to take out video cards.  Just mine on fewer GPUs at once and adjust the number, to find the maximum number that will stay stable.

Keep in mind the total watts does not matter, only watts on the actual 12V rail (some PSU's have multiple separate 12V rails) you are running PCI-E cables off of.  Good PSUs will show the breakdown in a chart on the PSU itself - how many watts on each 12V, how many watts on 5V, etc.  Also there is a limit of (3, I think) molex-PCI-E converters before you over-amp your molex.  Motherboards also have a limit on a separate 12V that feeds the PCI-E cards from the slots, if you have too many cards it will overload the motherboard (and usually overheat wires in the ATX motherboard power connector).   See:
https://bitcointalk.org/index.php?topic=8847.0  (4x 6990 thread)
http://blog.zorinaq.com/?e=44  (linked from above- describes modding your PCI-E extenders to connect 12V pins direct to the PSU, to avoid overloading the motherboard)

The easy solution is to do as I said above, turn on one GPU at a time until it crashes, then run with one less GPU for 24 hours to make sure it's stable.  IF this works, then buy a 2nd PSU, and hook it up using one of these:

http://www.frozencpu.com/products/11742/cpa-167a/ModRight_CableRight_Dual_Power_Supply_Adapter_Cable.html

edit:misread. Let me redo my math.

Definitely under dimensioned PSU. At stock speed a 6990 requires 375W. When you flip the switch, it goes to 450W. A 6970 is rated at 300W at stock speed. Overvolted and overclocked its probably closer to 400W (power consumption increases exponentially with voltage), but lets say just 350W on average for all 3.

450+3x350=1500W

We havent even taken in to account the CPU, motherboard, ram, hdd. Nor have we considered the fact that most PSU's do not achieve their rated power.

Yeah, definitely a power thing.

For one thing, sucking up 1500 watts is about the equivalent of running a hair dryer constantly... or one of those box room heaters... or something obscenely power-hungry like that. I mean, we're talking like, "dude, you'd better check your power cord to the wall outlet and make sure it's a couple gauges heavier than normal" kind of crap. I'll bet you it gets warm, if not hot. So in light of that topic of conversation, you really need to make sure you've run the ELECTRIC BILL analysis on this kind of completely ludicrous rig... it's going to cost you almost triple-digits on your power bill, so you'd better be CERTAIN you're going to make that back in Bitcoin. Not to mention, if you use it indoors and you need to run air conditioning in that area, it's going to cost about 1.5x that amount in electricity to remove the heat produced by the PC. It's no joking matter. It's summer here and I run my mining rig literally, outside on the porch (2nd floor = great anti-theft), to offset the cooling problem. And I'm still barely breaking even on the power bill, if that much.

That said, your GPUs are stupidly over-powered. Knock them back to pure stock and you should be fine. You also need to make sure:

1) Your CPU usage is ZERO PERCENT while running miners. Any indication of CPU load is typically a rat's nest of API version, driver version, miner settings, etc., that results in any amount of CPU usage caused by a GPU miner. This was a long struggle for me to find the best way to solve. Basically it boils down to one thing: start with low aggression settings, and test each setting for 10-20 seconds to see which one starts causing CPU usage while you're seeing a "Mhash/sec" reading (actually running, that is). If it causes CPU usage, knock the aggression down to the last one you saw 0 at. And drivers, evidently there are some issues with Catalyst 11.7 and 11.8 (the latest), so you ought to move to either 11.6 (browse AMD's archive list), or find the 11.9 beta at guru3d.

2) Always keep your eyes on each GPU's temperature. With that many GPUs, god knows how you fit them in the case. Fans don't move air when they're in a vacuum, so be sure you either have a handful of fans COORDINATED to push air from the front of the case through the back (pulling air in is always easier than pushing it out, it seems), or just leave your case side off and direct a blower fan at it or something. But I can tell you one thing: those GPUs were NEVER designed to operate at full-capacity, right next to each other, for an extended period of time. You've got to make sure you stay on top of their "health" to make sure they stay working properly.

3) Clocks. First of all, don't "just" overclock. Mining is a very unusual situation to put a GPU in, so it doesn't need the same uber-high clock speeds that 3D rendering usually requires. For example, on my 6770, setting the memory clock (default at 1200, I think) to 300MHz actually puts the GPU in some sort of timing mode that essentially super-charges its mining speed, but drops about 10 C off its running temperature. Maybe it shuts down some unused clock modules or something. Whatever it does, it lets me run the thing at 950MHz/300Mhz (core/mem) when its default is more like 850/1200, and bangs out an extra 30 Mhash/sec while keeping the GPU core cooler. Find the right settings, search around, and don't just "move the slider up". And FFS, put the voltage back to stock, that's a freakin' sweet way to nuke your cards in no time...

4) Clients and settings. There's a HUUUUGGEEE difference that can be made between one client and another, and between one parameter and another. For example, my GPU goes from 211Mhash/sec to 160Mhash/sec when I just remove "worksize=128"; the kernel (currently using a modified phatk posted here somewhere, but very similar to the phatk2 provided with Phoenix) defaults to a worksize of 256 and my GPU only has a 128-bit memory bus (it doesn't know that). Performance goes through the floor. You may mess your pants when you see some 300-odd Mhash/sec, but what you don't know is that it could be straining itself with some bad settings and you could be seeing 400 if you played around a bit. "BFI_INT" is pretty much a necessity. Play with "VECTORS"/"VECTORS2"/"VECTORS4" in combination with different "WORKSIZE=" (64, 128, 256) values - the "vectors" values mesh with the given "worksize" to produce each sort of work "chunk", and finding the right combination is key to a smooth-running system.

5) You don't need a new power supply, just quit sucking power out of the wall like it's going out of style! Run the numbers - consider that 1500 watts continuous is what you're drawing (since we already know we're blowing past that as it is), run that as kilowatt-hours (kWh), which is approximately 1.5kW (long form, "1.5 kWh per hour"), and run that out to running 24/7 for a month. 732 hours in an average month, so we're talking... 1,098 kWh for your rig each month. And we plug price into it at about my average power rate, which is $0.15/kWh, and... *click click*... yeah, that'll run you $164.70/month in power to the box alone. Remember what I said about air-conditioning; when you factor in the $247.05 for cooling the house from the heat generated by the rig, that's $411.75 a month. 'Ya sweating yet?

I dunno, maybe I tldr'd here, spent 20 minutes writing this crap for one guy's rig, but dude, seriously, 2000 bucks? I was sweating spending 100 on my 6770 and had to split it with a friend ;) If it helps you any, there's an address in the sig that could help me buy a compliment to my single 6770!

edit: I may have "duh, I already know that" on a few topics regarding clock, but I went back and noticed you said it was at 180MHz? Did you get that from somewhere? I read 300MHz for mine, and if I even vary from that a slight bit, I either get a power-consumption (heat) hit, or I get a performance hit - 300MHz is the "sweet spot" for the thing. Good to be right-on the number, but even better to run it through a meter and see what it does to your power consumption. :)

Well, this isn't the first time I've built a computer. ;) Also, the 4x GPUs fit in just fine, the case definitely has enough slots, as well as the mobo. If you've ever put a bunch of 69XX series cards in a case before, you'll notice that there's practically no clearance between cards -- so I made some small 2-3mm spaces to place between the cards for a little better airflow.

The 180MHz comes from me testing the rig based on MH/s performance from my 6970 miner cards. I was able to clock the memory down all the way to ~180MHz before I started noticing the MH/s performance started to plummet (why is my 920MHz 6970 mining with phatk @ 300MH/s?!) Lowering the RAM speed for the GPUs seemed to significantly lower GPU core temps as well, and I would assume lower the power usage a bit, so win-win. And I didn't "just overclock" the GPU's, I tested each card painstakingly based on benchmarks and reviews I had read about around the internet to get an idea of stability vs. speed vs. power usage, etc. I've put in the leg-work here to find what works and what doesn't for these cards.

As for electricity, I have a deal worked out with a friend who gets unlimited electricity (lets not dwell on that topic and what it implies) where I'll basically store the rig at his place in an empty room by itself, which has an AC vent and stays fairly cool, for maybe $10-15/month. A small fee, no? The rig would connect automagically to his house over WiFi, and would be plugged into the wall. He'd close the door, and the fans would be running @ 100% all the time. Really, I've done my homework here in terms of automated setup, and getting things installed and running with Linux. The only problem -- and its a big one -- is GPU stability. And yes, the tower itself is connected directly to the wall with some lower-guage wire. Very thick. It has to be.

Those 4x fans I mentioned are high-CFM fans, with 2 in the front of the case pulling air in, 1 on the back pushing out, one on the top pushing out, and one on the panel side blowing air directly on the top 3 cards. There is a LOT of airflow in this case.

I'd like this to generate 2200MH/s -- now I know thats purely idealistic but thats how I planned it from the start when I was shopping for parts. I guess I could run everything at stock, but I'd really love a bare minimum 2000MH/s. Electricity isn't a concern for my situation (at the moment). I just need to stick this somewhere and let it run with 100% fans 24/7 at sub-90C temperatures. Also, if you're clever (read: clever), $2700 to drop on a rig like this isn't that insane. Let's just leave it at that.

If all I need to do is power the 6990 with its own 500W power supply for stability, I have no problem buying one from Newegg to make this work. I really want this whole thing to work. I'd like it to work without having 2 PSU's (hence why I bought a 1500W beast to begin with) but I'll certainly invest a few more dollars in it if I have to. Especially if those extra dollars let me hit 2100MH/s or so.

EDIT: I'll look into the aggression/CPU usage advice, hm.. I use VNC and SSH into the machine sometimes, might that little big of CPU usage trigger an excess usage of watts that my power supply can't deliver? :?

EDIT2: Just ran with everything on stock, all switches set back to original low-wattage position, set all the GPU memory speeds to 180 (low!), and after 5 or so minutes the whole rig crashed. Defective PSU? 375 + 300 x 3 = 1275W from the GPU's, which leaves enough wiggle room I think for a non-overclocked i3 and RAM and an SSD. Not sure what to think about this now. :/

Wow, OK, you've definitely got shit planned out proper! Great work there. Usually the image I get of someone with 4 GPUs wondering why their power supply clicks off, is summarized by the phrase "trust fund baby", haha... seems you don't exactly fit that bill!

Well, you've taken care of the clocks, so that's cool. No, I'd think VNC wouldn't affect it that much, since I use TeamViewer to remote into mine, and the wattmeter barely flitters a watt or two. However... I'd like to throw one far-fetched idea out there just for curiosity. Linux, to me, strikes nothing but images of piss-poor graphics performance, glitchy kernel-module drivers, half-written software, and elitist "support" from anti-Micro$oft fanboys. I dab in desktop Linux every now and then (server Linux most of the time), and every time I put Linux on a desktop, I half-regret/half-pity it - despite hours of Googling, tweaking, compiling, configuring, researching, and downloading... it always runs like utter shit even on capable hardware and "proper" software. That said, have you considered putting Windows 7 to a test on there? I think it'd be worth a try with all its power-management features and all :)

Now if only I could get my shit working proper. :'(

Tomorrow I'm gonna flip the 6990 BIOS switch back to high-wattage mode and let it run all day mining by itself with a bit of overclock. Should push the PSU, but should definitely not cause a random shutdown. If it randomly shuts down, I probably have a defective PSU. For good measure I'll probably underclock the CPU and RAM a bit too.

I'm still welcome to suggestions and insight and such. I can't believe it still crashed after I returned everything to stock and flipped BIOS switches back to low-wattage mode.. ???

I definitely recommend getting a Kill-A-Watt to measure how much you're really pulling.  Remember to multiply the measurements by 1.25 (the PS is only 80% efficient).  You may find that the estimates of what the cards pull at stock clock vs overclock are wrong.

90% chance you're hitting the thermal limit, not overcurrent or undervolt limits.  Put the PS into free air and use another fan to pump some more air into it.  You're probably right on the edge and it just trips whenever the room's a little too warm.

Why not pull a PS from another computer to run one of the cards and see if that helps?

There's no point underclocking the CPU.  It made sense on fixed frequency CPUs years ago, but all the current ones have frequency scaling.  At the most, just lock the scaling at the slowest value to prevent power surges.

@Revalin: Don't know where you got the multiply by 1.25 thing - not only would that represent a "75%" efficiency (125% correction), but... the Kill-A-Watt has no care how "efficient" the device it's monitoring is, it calculates how much power is flowing through it and that's the only part that counts! In fact, the KAW actually *does* calculate efficiency, and it's called "PF" (Power Factor), represented as a number between 0.00 and 1.00 - a PF of 0.98 means it's 98% efficient (and most PC power supplies are, since they use PFC to reclaim the wasted energy in the switching cycle). You shouldn't be doing any manual calculations with the numbers given to you by the Kill-A-Watt, plain and simple - it tells the facts as the power company sees them. :)

Agree on pretty much everything else though. The PSU may not be pushing enough air through it - I'm pretty certain most of these PSUs were never actually *designed* to have a full load! I think a good test might be to fire up one miner at a time, giving the PSU a chance to get its cooling figured out for 3-5 minutes after each one. Maybe that'll help?

Sorry, multiply by 0.8.  I was going the wrong way.  But 1.25 is the correct factor going the other way:

100 watts AC * 0.80 efficiency = 80 watts DC
80 watts DC * 1.25 efficiency = 100 watts AC


That's the part that matters for your power bill.  However, if you want to know if you're exceeding the power supply's rating, you have to take efficiency into account to estimate how much power is being drawn on the DC side, which is what the PS is rated for.


Power Factor is not efficiency at all.  It's a measure of how bursty the power usage is.

An incandescent lamp has a PF of 1.00, since it draws current in a perfect sine wave with the voltage.  Induction motors pull current out of phase with the voltage, so they have a low PF.  Old power supplies draw power in bursts around the peak voltage, so they have a low PF.

Those bursts mean you need heavier wiring than your average current requirement suggests, since the peak current goes much higher.  It also means the power company needs bigger transformers because they're rated in volt-amps (IE, limited by the peaks), not watts.  As far as your power bill goes it doesn't matter since they're only measuring average watts, not peak volt-amps.


Agreed it tells it how the power company sees it, and there are no conversions necessary to understand how you'll be billed.

However you do need to convert if you want to estimate how much power is being pulled on the DC side.  The Kill-A-Watt has no way to know how much power is being wasted as heat inside the power supply.

Ahh... OK, I thought you were referring to the "how much it's going to cost you" discussion with the 1.25 thing. Absolutely right all around - the K-A-W has no idea how efficient the device is internally, but it knows how much power is being wasted back to the grid with AC phase "bouncing" (I did research on that stuff too :) ). It's still a measure of efficiency - if you've got something with a 0.75 PF, you may be using 100 watts to only get 75 watts worth of "energy" out of the device = inefficient! Crappy "brick" power supplies tend to do that.

But yeah, you're right on the 1.25 = 80% correction... I never did take any advanced math classes (trig, statistics, etc), so most of the number-shuffling I do is "um, well, putting the number together like this seems to make sense" sort of thing... heh.

FYI, this is what it says on the PSU:

http://www.xbitlabs.com/images/coolers/1000w-psu-roundup-2/9p7s.jpg

Thats "only" 1320W on 12V lines, which is all that GPU's use.

Even at stock speeds (edit) 300Wx3 + 375W = 1275W for the GPU's alone. Granted, thats TDP, while mining at low memory speeds it might be lower than that, but you have other devices that need 12V, not in the least the CPU.

I agree. This is why you shoulda went with AMD, they're less power hungry. You should try them all at stock first and work up. Silverstone is a good name brand. I'm sure it can hit 1600w or so over the rated wattage.

+1, u need more power

Nope.  Power fed back will just be consumed by other devices in your house, thus reducing the amount pulled through your meter.  It's not wasted.  In the unlikely case that you have a huge inductive load (very large motors), your power meter subtracts the amount you kick back.  People with solar arrays see this all the time: if they generate more than they use, the meter literally runs backwards.

Anyway, in the case of crappy power supplies, they just switch between using a burst and then nothing.  They don't kick back to the grid.

You are kidding right?

http://images.anandtech.com/graphs/graph4524/40753.png

Not that it would matter a lot in this case, but that doesnt make you any more right.

I also think you missed the PSU is rated for 110A max combined on 12V.

Yeah, I'm with the "you're kidding, right?" thing with the AMD comment - AMDs are power-hungry whores compared to Intel's offerings. Intel was a good choice here.

But now that you posted the label... SILVERSTONE?! Seriously? Mid-low grade garbage in this application - good for pretty much anything except being fully utilized. Get a Thermaltake, Antec, or I hear good stuff about a company called PC Power & Cooling (though I've never seen their products in person), who knows what else. At 1500 watts, the PSU would have to be VERY professionally designed - trying to regulate and process that much power and stay smooth requires some super-serious engineering that some cheap Chinese piece of crap is not going to be able to stand up to. Yeah, I'd say your PSU is the weakest link... go return that pieceofcrap and get a serious PSU. I'd suggest running it by us here first ;)

If you look up any serious reviews of the PSU, it actually does very well, its getting top grades in all reviews Ive seen, including [H] and their torture tests. Here is the conclusion:
http://www.hardocp.com/article/2010/09/01/silverstone_strider_st1500_1500w_power_supply_review/9
I really dont think its a bad PSU, but you cant expect a PSU to deliver more than its rated for. To run this many powerhungry cards, he needs a second PSU, "1500"W (which is actually 1300W where it matters) isnt enough for his config. Ditch a card or buy a second PSU for the GPUs.

*squint*

srsly? Feel like I'm reading an alternate reality here. SilverStone, far as I've known is a no-name Chinese knockoff brand... and they're getting reviewed professionally? This is freakin' me out a bit. Maybe I'm wrong about the no-name Chinese thing. I dunno. I just wouldn't trust 'em more than I'd trust a real, established brand...

I mean, a 1500W PSU should weigh like, 30 pounds... o.o

It does weigh like 30 pounds. ;) I remember it being pretty heavy when I pulled it out of the box.

I put a lot of thought into reliability and build quality when I was shopping for all the parts. I did my research, and I remember reading that this PSU had been tested and was a high-quality, solid 1500W supply, even in a "hot box" testing environment. It's a shame it can't keep up with the load. It's also a shame there isn't a better, higher-wattage Gold/Platinum certified supply out there for me to blow all my money on.

I think I have an old 520W KINGWIN modular power supply lying around somewhere.. Was going to give it to my parents so they could use it in a simple office rig I was building for them -- sorry mom & dad! -- but I might just set it in the empty DVD slots in the mining tower and connect up the 6990 so it has its own private power supply. I don't think this position will compromise effective PSU cooling since there is just SO MUCH airflow in the case. I think it will fit in just fine too.. the mining tower case is certainly big enough, and that PSU isn't all too big. Maybe I'll run the power cord out through one the rig's unused water-cooling holes? lol. Not an ideal setup I know but I really want this rig to be set up as a single unit, just plug it into the wall, close the door, and its good to go, helping me pay for rent. ;D

BUMP & Update:

I've managed to jam the 520W supply in, fitting it snugly where the 5.25" drives would go. I've slotted the power cord through one of the watercooling holes on the back of the case.

Right now I'm waiting for a dual-PSU 24-pin connector in the mail (so that both PSU's are turned on when the whole computer is turned on) and the 520W will power the 6990 by itself (or a single 6970 if that would be easier for a 520W supply to power). The 520W supply is maybe 4 years old, was great when I used it with my 8800GT back in the day, and it only has some 6-pin connectors. :( So I'm using a couple dual-molex-to-8-pin adapters that came with the 6970's with 4 separate molex lines from the 520W to power the 6990. Since I'm splitting it up so that the whole thing is powered by two internal PSU's, I plan to overclock all the cards and aim for at least 2100MH/s, if not slightly higher. Heat exhaust be damned!

Will post pics once the cables arrive in the mail this upcoming M/T! Its all finally coming together! 8) Am still open to suggestions/advice about the rig, interpretations of power requirements, etc.

You can turn the power supply on for testing by putting a paper clip between the green wire and any black wire on the motherboard connector.

I had to read the last post 3 times to find the relevant part of his reply where it was even implied that he was having trouble finding out how to switch on the secondary power supply... I was like, "I don't think this guy's noob enough to not know about green-to-ground to power on", but at the same time I had to look over your post like, "wait, I've seen this guy before, he's not one of those non-English-speaking-so-they-don't-follow-the-thread-context noobs dropping replybombs* in threads... sooo...

... Then I found it:
Ahhhh... wow, he really DOESN'T know!

Dude, just jump green to ground. Look in the ATX connector for the green pin. "Green = PwrOn" used to be labeled on those power supplies but they got lazy... just to be safe I'd actually recommend powering a SATA hard drive/SSD off that power supply as well, just to give the +5v line something to do.

In fact, merging power plugs of both PSUs using a "dual" splitter cable is probably fuck'a dangerous - you'll then have two power supplies competing for voltage regulation. Don't put two independent voltage rails (e.g. "+12v" of one and "+12v" of another) together. They maintain their regulation by adjusting their load to match a certain level (thousands of times a second), so if there are two self-regulated supplies feeding into each other, one could blow the other up by backfeeding it - theoretically. It's likely never happened, but PSUs have protection against that happening (that doesn't make it any more "proper"). Just jump the green pin to ground and call it a day ;)

* - replybomb (n.):
Example:
joe: hay when i boot windoes with this new driver i installed it gives me an error saying the file is missing or currupt hurp?
jack: i seen that before somewhere... hit f19, stand on your head, hold mouse cursor by the tail and spin the display in circles and post the error code it gives you
joe: haha that was fun 0xDEadbeEF
jack: sweet, ok, you can fix that by inserting a slice of bologna in the cd-rom drive and singing glory hallelujah in b-minor.
joe: holy shit it worked
mark: U CAN BOOT TO SAFE MODE BY PRESSING F8 AT STARTUP AND DELETE ALL YOUR COOKIES!!

You got it right the first time :)
Im sure he is ordering a cable like this "Dual PSU 24-Pin Adapter Cable":
http://www.performance-pcs.com/catalog/images/products/Dual-PSU-Cable_01.jpg

Guess what it does :)

I know about shorting the two pins, but I don't want a paperclip sticking out of anything related to electricity if I can help it. ;) So I'm ordering the cable out of principal. But I guess I could get a coated paperclip and strip off the ends and short the pins, but idk, can you blame me for being wary of sticking paperclips near electrical pins? lol

It's called "wire" ;)

But actually, the paperclip is "ground" - you can actually just screw the paperclip down to one of the GPU bracket screws, and plop the green wire smack onto the (now mounted securely) paperclip. Instant bird stoning! But bird stoning is mean, it hurts - can't we kill bugs instead? =P

also: oh god I love that dual adapter, great freakin' idea. Usually chinese shit-shop components blindly shove I/O pins into any combination people would be dumb enough to search for (creating a product based blindly on demand alone - ugh! what next, HDMI to SATA adapters?) - but clearly that adapter is made by someone that understands its purpose ;) Good one!

I use the paperclip for testing...
if yor woried about the paperclip touching anything else...
the just wrap tape around it...
if you don't want sticky tape residue on the power connector...
put paper or a plastic bag...
then tape that.
then you will feel a bit safer while waiting for your connector...

fyi, I run the same power supply with 4 6970 GPUs...
using a kilowatt meter i pull about 1100W

Not at all, better safe than sorry.  :)

But in this case it's OK.  The black wire is ground, the green wire is an input.  So the paperclip is completely grounded already and nothing will happen if it brushes the case or something.  Just don't let it touch any live wires (the same as you shouldn't let live wires touch the case).

On my test bench power supply I just wrap a piece of blue masking tape over it.

+1, it's all good if you use that kind of cable.  Just don't use one that connects all the pins.

not to hijack this thread
I plan to make my own... i got 2 24Pin Power Extention calbes... for almost cheaper then if i was to order from the US (& shipping)
looking at the picture ...only thing that is connected is the black and green wire... which makes cents...
however i just want o clarify that there isn't a third wire. looks like shadow... but i just want to make sure.

Yep, that's just a shadow.  All you need is the green wire plus any black wire.

Hmm.. thats a tad less then I would have expected. With 85% efficiency that means the PSU is delivering "just" 935W. Assuming the rest of your system is comparable to his, changing once 6970 for a 6990 like the OP adds 75W max (if everything back at stock speed). Although its close enough to the stated specs to make me uncomfortable, it makes you think the PSU should be able to deliver that.  OH well, for the price of a cable its still a theory worth testing :).

I have a 6990 and 4 5830 running off of an Antec AX1200
its pulling 1065W from the wall
if i disable the 6990 from mining then it pulls 746W
so that a difference of 319W (not sure what the 6990 pulls when idle)
all Idle it pulls 286W from the wall.

So topic bump and update here,

I've hooked it up so that the second PSU, the 520W, is inside the tower and connected up properly. I've shorted the power-on pin and ground pin with a paperclip. I'm powering the 6990 with 2x dual-molex-to-8-pin connectors. The 520W supply has 3 molex lines (a cord with a bunch of molex connectors) and a SATA line, which I used a Female-Sata-to-Male-Molex on, so I have 4 molex lines. One molex from each line is connected to one molex slot on the molex-to-8-pin connector. IT SHOULD WORK JUST FINE. But there are issues.

• If the 520W PSU is running before the rest of the PC is on, when I turn the main PC (by pressing the main power button), the 520W PSU shuts down and I have to fiddle with the power-on paperclip to get it working again.
• When I've actually gotten the whole system up and running in Linux, where the OS can see all the cards and report temps etc, when I actually set one of the 6990 cores to start mining with phoenix, the 520W PSU shuts down.

 ??? Why would it shut down as soon as I increase the load on it? Doesn't make sense. This thing is rated for 520W.

EDIT: Just switched the 520W from powering the 6990 to powering a 6970 set to low wattage BIOS switch position. Same symptoms. Ubuntu will start booting just fine and then the 520W PSU will just shut off. I have to play with the paperclip a bit to make it start running again. :/

it may be rated for 520W but that doesn't mean an individual Rail can take that kind of load...
what is teh max wattage in teh 12v per rail.
it may not be a single rail.

Hm, that's a good point. Let's see here, from Newegg: http://www.newegg.com/Product/Product.aspx?Item=N82E16817121013 ,

Output
    +3.3V@32A,+5V@42A,+12V1@18A,+12V2@18A,
    -12V@0.8A,-5V@0.5A,+5VSB@2.5A

So it looks like it has 2 12v rails.. Fgsfds. Hm. I might actually have to go and buy a new power supply after all. :/

well its safe to assume that 1 of the 12V rails goes to the motherboard connector.
the other goes to PCIe and molex connectors.
U may be able to run a 6970 off of it.
not sure....
then u would have enough power to run the other 2 6970's and teh 6990 off of the 1500W PS

worth a try...

Any chance that there's an 8-pin EPS to 6+2-pin or 8-pin PCI-e adapter out there? The EPS rail definitely has enough juice, the pins are just wrong. And looking at this power supply, it looks like the other 12v rail is the dual 6-pin PCI-e rail, which I guess I could get a dual-6-pin to 8-pin adapter for. But it really all comes down to whether or not an EPS rail adapter exists.

???

You can plug 6 pins PCIE connector in to a 8 pins "socket". A 6 pin is rated for 150W. x2 =300W. Add to that 75W from the motherboard, and it should be plenty for a 6970 at stock speeds.

You havent mentioned though, if you plug out at least one card, does the system work fine under load?

that kingwin psu. does it have minimum power requirements on each rail? like you must have 1 amp on 5v? many older psus will not run stably unless you meet minimum draws too. check the label on the psu.

to get around that some folks plug old hds or opticals in.

https://i.imgur.com/dfAJT.png

I see information in the manual about minimum power supplied, but nothing about minimum power required. And its not too old either, I only bought it in '07.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817121013

Edit: I'm wondering if maybe the way the airflow of the rig is set up is leading to a robbing of airflow through the 1500W PSU. The rig has 4 video cards in it: 3x 6970's on top, 1x 6990 on the bottom. The 6990 intake fan sucks up air in order to cool it off. I have all the fans of the video cards running @ 100%. The 6990 intake fan is directly above the PSU intake fan. I wonder if this is messing with the flow of cool air through the PSU, and leading to overheating and random shutdowns? Will post pics in a little while.

So, where does one learn apparently elementary things like "ground it with a paperclip to start the PSU?"

I was thinking about building a rig myself, but decided not to because I am concerned about the viability of the bitcoin market.  This thread is making me glad I decided not to simply because my knowledge of electronics is so rudimentary.

that "min" column... that is minimum draw needed for it to operate correctly. thats what Im talking about. you need 1 amp on 5 v and 0.3 on 3.3 volt.

without that it will not regulate properly, and when you turn on the other psu something goes over/under minimum and its protection kicks in.

try plugging a couple hds in it and try again.

http://imgur.com/a/hBhuI#7oxAx (http://imgur.com/a/hBhuI#7oxAx)

Any chance the low clearance between 6990 and 1500W PSU and the opposing airflows might have something to do with random shutdowns?

read this again.

YOU NEED A MINIMUM DRAW on 5v and 3.3v or it WILL NOT operate correctly.

sorry for the bolding but that is your answer.

No, read my question. I'm talking about something completely different.

I understand the likelihood that I need to plug in something in order for the power supply to function properly, powering a 6990 or 6970 by itself. But those pictures don't have my 520W in it. My question goes back to the 1500W PSU in the case, which is shown in the pictures. The 1500W has shutdown randomly for full-load overclocked and stock speed GPU configuation. My question has nothing to do with the 520W supply right now.

I'm wondering if the 6990 is robbing enough airflow from the bottom-mounted 1500W supply to cause it to overheat.  :-\

Can you first let us know if the rig is stable with 3 cards?

As for the PSU overheating, I kinda doubt it, but you could just pull it out and find out.

ahh. my apologies to you then.

however it was right after my post and you hadnt mentioned anything about it, I figured you didnt believe the post.

Post a picture of your setup...
this will give us a better idea of how your cards affect everything else

Sure, will do. Gimme a few minutes.



EDIT: Alright, I'm running the top 3 cards right now at full load, with the bottom 6990 sitting idle and with its fan set to a lower speed. Current clocks: 900/180, 950/180, 880/180, yielding a lowly 1220MH/s. :`(
Typically when the whole thing crashes, I can feel the metal plate on the back of the PSU feel REALLY hot. Right now it only feels warm. We'll see! If it turns out that this is a general problem for bottom-mounted PSUs.. well, I'll just kick myself and order a new case with a top-mounted PSU I suppose. :(

question...
are you leaving your side pannel off?
reason i'm asking is the 6970's will dump all its heat out the back...
but the 6990 will dump its heat out the back and the front.

but i don't think your powersupply is over heating...

also does your mother board have an extra molex connection for power?
the PCIE bus will supply 75W of power to each video card...
thats 300W alone that the motherboard will supply....
mind you i don't know if the video cards pull that much power from the PCIE when they have extra power supplied via cables.
just a thought...

did u get a chance to hook up one 6970 video card to your 550W psu?
if so how did that go?

Nope, I only took the side panel off to take the pictures. Also, leaving the side panel on provides a lot of extra cooling to the top 3 card slots, since there's an 80mm fan mounted in the side panel that moves a lot of air onto the cards.

And yeah, the extra molex is attached.


Like I said, the PSU would just shutdown randomly unless I fiddled with the paperclip again. Something wasn't working right, which is why vapourminer was suggesting to plug in a few hard drives. Which I'll probably do later tonight after I've left the rig mining with 3 cards a for a good long while, monitor the temps, etc.

Still open to suggestions/observations! ???

EDIT: It's been running for 1.5 hours at full load. Temps for the 3 GPU's running (all 6970's) are <= 80C. Good stuff. I ordered a Kill-A-Watt from Amazon, should arrive Tuesday, will give me a good idea of how much electricity is actually being used. If the system is crashing @ <1400-1500W of usage, either the PSU is defective (and needs to be replaced under the 3-year warranty) or the 6990 @ 100% fan speed is stealing too much airflow from the PSU and causing it to overheat.

just a thought...
try hooking up the 550PS to your motherboard...
that will then power the board and save on using power from the 1500W PS
leave the 1500PS plugged into the harddrive...

and plug in one of the 6970 GPUs to the 550W PS ,
or perhaps split the load between the 2 PS where only 1 PCIE power connector is in the 550W PS and the other comes from the 1500W

myself i'm running out of ideas...

I have noticed on occasion my 1500W PS on shut down refuse to start back up... this was on shut down for maintanace so the power down was for a short time...
then afterwards it would power back up just fine... (heat of the summer and the room was pushing 37-39 degrees...

NLA,

Man, this has been an epic saga getting your rig to work! Hang tough, man. Just wanted to say that before you buy a new case for top mounting the PSU, you might try just turning it upside down so it is pulling in cool air from underneath. Since you have an oversize PSU, you might have to cut a hole for the intake, but you might have to do this for a top mount case too (I'm really not sure to what extent cases are designed for oversize 1500 watt PSUs). Sorry if someone already suggested this - haven't had time to read through every post. After my experience with mining in a case, I would just forget about the case and go with an open air  rig. I realize this is probably really unappealing or simply not an option for you, but cases are such a hassle when you are running 3 or more GPUs at full load. I started with two 5850s in a case with great airflow, and even then cooling was an issue. So when I expanded to four, I lost the case and haven't looked back. And I've grown fond of this funky industrial tech art object sitting in my house, lol.

ACtually looking at your pictures again, doh, yeah your case is too small:

https://i.imgur.com/CG3Yfh.jpg

clearance between the bottom 6990 and the PSU is really not enough since the fans are fighting each other, and theys suck in each others heat. Particularly with the side panel on.

Im assuming you wont run this noisy space heater in your study, but somehwere in the basement or wherever, so Id just leave the side panel off and pull the PSU out and put it next to the case. Problem solved most likely. If you must fit everything in a closed case the above advise of turning the PSU upside down and cutting a hole in the bottom is a good one (if you give the case some bottom clearance), but honestly you want a bigger case, or none at all

Hooh my GOD... dude, that case is WHAY TOO FUCKING SMALL for those cards... :o :o

And yeah! Your second PSU should be powering 2 of the cards and a hard drive (to provide a 3.3v/5v load), not the mobo or anything else! It MUST start up at the same time (or shortly after) your M/B so the cards don't get brainfucked by the lack of a M/B power load or bus clocks (and so they don't back-power the board itself).

1: are you fucking serious, take that bottom card out. NOW. That's why your power supply is shutting down, it's NOT GETTING ANY AIR around that video card that's directly blocking the PSU fan...
2: "(!) Read the..." (and likely "remove this" somewhere on there too) - ummm.... did you read that tag? o_O
3: please ship me your rig so I can do it right >.<

lol, yeah I've kinda suspected for a couple days now that the real issue might be that the case is just too small and the PSU might actually be overheating, yeah. And that caution sticker is the warranty-destroying sticker over the GPU BIOS switch. I'm leaving it on so that I can keep the warranty in-tact, but I'm using a small (small!) screwdriver to adjust the BIOS switch as I see fit. ;)

I think I can still get away with this setup though. Assuming that power isn't an issue (which I'll figure out Tuesday when the Kill-A-Watt arrives from Amazon), and the PSU really is just overheating, then my "fix" might actually work here. If the PSU is overheating because its HUGE fan isn't moving enough air through the PSU, why not just increase airflow through the PSU with an external fan? So right now I have a small fan pressed against the power supply grill on the outside, and it is moving a LOT of air through the PSU. I can feel it sucking a lot of warm-hot hair out of the PSU.

So interestingly enough, before whenever I would try to have all three cards running simultaneously mining, and the cards were stable temperature and clock wise and they didn't crash (which would reduce power usage since the GPU would no longer be mining) then the whole rig would shutdown after ~4-5 minutes. With this little fan on the external side of the PSU pulling more air out, I've been running the whole rig mining with all cards for at least 20 minutes now, no issues. Here's what I'm currently looking at right now over VNC:

https://i.imgur.com/oFS50.png

And I think the clocks are @ 935, 970, 925, 830, 830 right now. Adapter 1 is a bit warm, so I could probably reduce it by 10MHz or so, and the bottom 6990 (Adapter 3, 4) is hanging around mid-80's, so I could probably increase it to 850.

Assuming the PSU doesn't overheat, I think I could actually get away with this. :-X

Ah shoot, it overheated and shutdown after 45 minutes of mining with the small fan to help move air along, as opposed to 5 minutes without the small fan. Well this definitely suggests to me that this is a temperature issue. :/

I've been looking through Newegg, and this case: http://www.newegg.com/Product/Product.aspx?Item=N82E16811112159 looks like the case I'm going to order. Plenty of fan slots, top-mounted PSU, 10 slots (so I can use a couple risers to give a 2 whole slots of space inbetween 3 cards..!) And I'm planning to replace all 4 of the 140mm fans with these: http://www.newegg.com/Product/Product.aspx?Item=N82E16835553003 .

I'm also going to warranty-replace the PSU while I'm in the mood for ordering new parts, for good measure.

Further ideas/suggestions/comments welcome.

Throw one of these in your cart too.
http://www.newegg.com/Product/Product.aspx?Item=N82E16882715001
If not just for monitoring how much load you're REALLY pulling out of the PSU (since you'll be dumping it on a friend who, blindly, somehow, doesn't give a crap), also good for around the house.

If you're not tied to Newegg, this one ships free, is the one I have, and tells you total/predicted cost as well as current power stats:
http://amzn.com/B000RGF29Q

I agree, that case looks decent.

80 C is "uncomfortably high", just so you can re-calibrate your "perception of numbers" mental logic. Better start cooling those things BELOW 80, if you want them to last any appreciable lifespan.

Replacing the PSU won't fix the problem if it's thermal. The ONLY way you'll get any better life out of it is if the new one's thermal sensor is actually *malfunctioning*, and not shutting off to protect itself. In fact, PSUs usually only kill themselves (shut off) when they're about to crack/melt the chips inside. You're doing some SERIOUS damage to your power supply as it is, every time it shuts down.

(BTW, the reason that LED stays on when the computer shuts down, is that there's no way for the power supply to communicate with the M/B. So the PSU just kills all its outputs, but the board is still holding "PwrOn" (green) low - the system management controller on the M/B still expects the PC to be "on", so those LEDs are being lit by the +5vsb (5v standby) power which is on another circuit in the PSU.)

1) Case with better power supply location.
2) Separate the GPUs. Fuck, man, I said this with my first post and it's taken 2 pages to acknowledge it? Those GPUs have absolutely no cooling going to them. You're f**king insane for thinking that would allow them to stay cool... srsly. Hell, you can see in the photos that the GPUs look like a solid block with no spacing (cooling) between them...
3) Probably don't need that second PSU if you can get some cooling to the PSU - it'll probably cool itself just fine if you actually let it have some fuckin' airflow...
4) srsly ship me your rig lol *fapfap*

You should also monitor VRM temps. Ive never had issues with GPU temps, but I always struggle to keep VRM temps sane. For ubuntu you could try this tool:
https://bitcointalk.org/index.php?topic=10228.0

It gives all 3 VRM temps on my card (5850), but Im not sure it will work with 6xx0 cards.

lol. I already ordered this model Kill-a-Watt from Amazon:

http://www.amazon.com/P3-International-P4480-Electricity-Electronic/dp/B001U638PM (http://www.amazon.com/P3-International-P4480-Electricity-Electronic/dp/B001U638PM)

and its what I've been referring to every time I've mentioned a Kill-a-Watt in the thread. Should arrive Tuesday.

As for the spacing between the cards, it doesn't look like it, but I have some spacers in-between them (some rubber erasers that I cut down to size) so there is something like 3-4mm spacing between all the cards. They're not just solid bricks.. although without the spacers they would just be solid bricks without any real cooling at all. Makes me wonder how the AMD engineers thought this was an OK design for a GPU.


Sadly, I already looked into this before, and it only works for 5XXX series cards, not 6XXX. :(

New Case + Fans should arrive in 3 days, Wednesday probably. In the mean-time, I'll be running the top 3 6970's with some pools I'm set up with so I can earn a little bit of digital money in the interim. :)

Then Id quickly install windows on a spare disk and use some windows monitoring tool for a day, just to see how your VRM temps relate to the GPU temps under load. If they are okay, then go back to ubuntu and forget about it.

Wow, so you just chunked down over $400 bucks on a case and fans? That's some serious commitment right there. Hope this is the final chapter of the saga.  :D

Yeah, I've already worked out the numbers. I have a good plan going on here, and I know what I'm doing. This is an investment. As long as I can just get this all up and running for a good long while, without overheating and such, I'll get out on top. 8)

Anyone out there use a different 1500W (or higher) PSU that they can recommend, if by chance the new case I've ordered doesn't help? ???

Right on, I hope you are right, and it's nice to see some optimism about mining; there's so much pessimism about it on the forum right now. Thermaltake makes a 1500w monster:

http://www.hardwaresecrets.com/article/Thermaltake-Toughpower-1500-W-Power-Supply/594

The review should give a pretty good idea of how good it is, but I doubt it is any better than the Silverstone.

Edit: oops, that PSU is only for the Euro market (230 volts)

Sure. The way I see it, the sooner that everyone who is a part of bitcoin realizes that all that panic and FUD does is 1.) lower the exchange rate of the bitcoin and 2.) lead to topics like BITCOIN IS CRASHING SEND ME ALL YOUR BITCOINS WHILE YOU CAN!!, the sooner everyone will get back to investing in bitcoins (read: buying 2-3 bitcoins every now and then) and the sooner the exchange rate will go back up to what it used to be. Bitcoin is a currency, and the value of currency is directly tied to people's confidence in it. More confidence, more profit to be had.

Also, a quick update: have been running the top 3 6970's for 24 hours now doing some pooled bitcoin mining, temperatures are stable in the low-80's. Sounds good to me! Can't wait for this case to arrive so I can get some proper cooling and I can finally get this horse running at full gallop!

Personally I think there's already plenty of confidence - that's why the value is as high as it is now.  What we need is more commerce which long-term will drive the value far more than trying to improve market sentiment.  The currency has to be useful to justify what you're making through mining.  Otherwise people are "investing" in a useless fiction.

+10
Even  the current price is 1% commerce and  99% speculation based on hope (or confidence if you prefer) that bitcoin will become more popular.

Bit of a small update as to where I am right now:

The BIG (like, XBOX HUEG) Lian-Li case arrived. I transferred over all the components, got everything set up, and closed up the case. After testing out things at stock frequencies, here's what I figured out: the sheer massive size of the case solved two of my problems -- the top-mounted PSU now has plenty of airflow and no antagonistic airflow currents to fight against, so it outputs exactly what its supposed to and doesn't overheat; the 6990, in the absence of the low-clearance with the PSU, now has plenty of airflow and stays at lower temperatures, even running at higher frequencies -- and unfortunately, introduced a new problem.. the 6970's are getting much hotter than they were in the smaller case. So the new case solved two problems and caused a new one. Well, s***. :'(

Then out of desperation, I took off the side of the case and mounted up a cheap window-mount fan that I have (http://www.drillspot.com/pimages/213/21333_300.jpg (http://www.drillspot.com/pimages/213/21333_300.jpg)), set it to max speed, and tried mining again. LOW AND BEHOLD, the temperatures are consistently, over the course of 30-45 minutes of mining, almost 20C cooler. It is spectacular how much cooler the temperatures were.

So since then, I've upped the core clocks of all the GPU's quite a bit, up to ~920-980MHz, and temperatures are hovering around the mid-70's low-80's. Power usage isn't too bad either (for whats in this rig), floating around 1350W according to the Kill-A-Watt. Current combined mining speed: ~2100MH/s, and by looking at the temperatures it looks like I might be able to hit just a little higher.

Sweet, glad to hear you got everything running. Not too surprised that you still had heating problems with the large case though. Happy mining!

Its a shame not too many cases out there are built for riser cards (making riser cards useless for most people), otherwise I'd put a slot of space in-between each card and go to town. It also doesn't help that the stock fans on this Lian-Li case barely move any air at all. :P

For anyone curious about the reality of differences between identical graphics cards, here's an example to take to heart: my top 6970, which has the most GPU core exposure to moving air (on the non-fan side), runs hotter than the cards sandwiched in-between it. It's running at stock frequencies, with the stock BIOS, and it hits 82-83C after a while even with the gigantic fan blowing on it, and its fan running @ 100%. No matter what position I put it in inside the rig, it always seems to run too hot. Before I had the big fan in place, it'd easily hit 97C after a few minutes. I'd RMA it and take a chance at getting a card that would run cooler and clock higher if I could have it by tomorrow. The card below it on the other hand, the best 6970 I have, hits 1000MHz with full stability @ stock voltage and stock BIOS settings, only hitting 77C. Card below it is somewhere in the middle of these two cards in terms of max stable clock, but temperature wise it runs cool.

Coulda told you that. Unless you separate those GPUs, there is no way for air to get into the fan that cools them. My suggestion: create some sort of micro-duct for the air to enter through, if you really need to keep them that close together. Maybe space the cards apart with something more than just a tiny eraser nub. They NEED CLEARANCE to get air into the fan... it can't suck air when a vacuum's been created.

I hate you just so fucking much right now. :D
(but that'll still only make maybe 1 Bitcoin every week or so... honestly I'm having trouble even breaking-even at 213MH/s for power consumption, not even paying for the card!)

Hey ding-dong, THE FAN IS WHAT COOLS THE THING. You can't just wave air across the outside of the GPU body and expect it to stay cool. The cooling is done with heat pipes and carefully designed cooling on the INSIDE of the card, with the whole operation set in motion by MOVING AIR from the FAN. If your top, exposed GPU has a big-ass GPU body blocking its air inlet, then no fucking shit it's gonna get hot no matter how much air you run across the "wrong side" of the card...

Hi. Then please explain how the two cards sandwiched between the top card and the bottom 6990 are cooler then the top card.

I've been over this before, and you can see in the pictures I posted of the rig, they're not just a solid brick of video cards.

https://i.imgur.com/CG3Yfh.jpg

I already told you many posts back that I have some erasers that I cut down to size and placed between the cards to provide space for fan airflow. And apparently yes I can wave air across the outside of the GPU body and expect it to stay cool because thats what I'm doing. Its ~15-20C cooler with the big fan in place. I've intentionally put space between the cards. You can see the spacing in the pictures. That blue thing there is an eraser in between the cards, forcing some clearance.

Even with the spacing in-between all the cards and all the airflow going on with the GPUs, which are running at 100% fan speed, the top card is still running much warmer than the others. It runs hot at stock temps, stock voltages, and stock BIOS, no matter what, and that was my point.

I'm looking at a solid brick of video cards, right there, in that picture, yup dee yup... that qualifies 100% as a completely solid brick of video cards. Not even joking. There is no "qualifying" amount of space between those cards to call it a ventilation gap. I call that a vacuum block. It's a brick. There's no air getting in there.

Have you seriously even held your hand in back of the cards to see what temp/how much air is moving? :P

I don't know much about setting up mining rigs, admittedly. But I do know that heat rises. Of course the top card is going to be warmer. I'd be surprised if it was any different.

Heat rises in air.  In metal it just spreads, and with heat pipes it very much moves toward the heat sinks.

The external fan is probably squeezing some air through the cracks which subsequently blows out the back of the card.

ah, 90 degrees huh? what are the temps the first 10 seconds? it shoots from 30ish ambient to 90 in 20 sec? Do you have good intake fans? like mine?
https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash4/s720x720/309240_10150308281471864_673676863_8195796_862212040_n.jpg

I noticed like 3-10 degrees difference with them on max. from 78-84c with fans off to 70-74 with them on max.

I think I might be wrong before.. 85% efficiency is pretty bad considering 15% ends up in heat. You should try gettting a 80+ gold PSU. If already tried all those suggestions, such as Huge window fan and default speed. Are you using afterburner or some mod to readjust the fan speed?

Have you tried cgminer? it's very configurable too. Has temp/reduction/OC features in the mining gui/commands.


85% vs. 92% efficiency is huge on a 1500 watt. psu. Oh you should try to use extra line or spacers on those cards at the end so air can go in each gpu. I have at least 1/2 cm between each card. yours looks like you got less then 1/2 cm between them. screw in the top card tight and position it a tad upward, and then you'll have some space. I'd say enought for a standard pc nut to get into. I'd probably put scythe kaze or any 100+ cfm fan blowing into the cards from the hard drive position and 1 fan blowing hot air out from the view of the side picture there.