Bitcoin Forum

So I own a bunch of these 400G fully populated units and they've been hashing for the past 1.5 weeks roughly. Today I get a 15 minute  BTCGUILD idle miner notification. I go out to check on the unit and its just flashing a red light on the raspberry pi. So I'm thinking that's weird as all my other units are plugged into backup APC smart UPS units and they are all still hashing away. I'm thinking ok a dead raspberry pi or a bad SD card. I restart the unit and it boots up and then an arc of light and it shut down again. Now I'm thinking WTF that's not good. So that's when I noticed the melted wires on the XFX 850w unit. Right now all my 12 rigs are powered via separate 1250 xfx gold psu's except 2 units. My other 2 units are being powered by the XFX 850w Gold and also a corsair AX 850w Gold. All my psu's being used are not being overloaded as you can see and they are all top rated power supplies as I don't mess around with cheap equipment or inferior equipment. I also have my cards completely heatsinked to remove the excess heat and my ambient room temperature is 15C or about 60F. The ambient air next to the rigs is 21C or about 70F. Cooling isn't an issue being outside temps are around 0C or 32F and I can open windows more of less depending on temps.

These units should all have 3 points of power to fill the amperage that this thing uses. That means the 2 6 pin pci express connectors should be used and also the other 12v screw connections should be used. I'll be making adapters for my other rigs that will have a 6 or 8 pin pci-e female end that goes to a ring terminal so I can screw it on. All my boards were 100% factory stock settings from megabigpower and these were the V2.2 H cards that have adjustable potentiometer on them. I brought this up numerous times in the bitfury thread which I'll have to post the link where I brought my concern about this.

Thread where I mentioned my concern regarding overloaded power connectors..post 198

https://bitcointalk.org/index.php?topic=287590.msg3228270#msg3228270

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Both 6 pin PCIe connectors and the wires are really hot on my fully populated BitFury rig (october version). My PSU is Corsair AX860W Platinum.

Using default chainminer settings I get ~640W power usage at the wall. To reduce the loads on wires and PCIe connectors I created a custom best.cnf file and force reduce speed to 51. With this settings I got about 560W to the wall and wires/pcie connectors are worm to the touch but as expected the hashing performance is lower.

Do you know where can we order some 6 pin pci express adapters for the 12v screw connections ?

You can order this part here, while its not the cheapest silverstone does make quality components. Then buy some ring terminals (blue or yellow colored is fine....just make sure the hole diameter isn't too large....Autoparts stores or hardware stores will have them) pictured below and solder it to cut power cable that you purchased. This should reduce the load on each 6 pin by 50%.

http://www.newegg.com/Product/Product.aspx?Item=12-162-036

http://www.google.com/imgres?imgurl=http://wiki.talkbass.com/images/6/63/Ring_terminal.jpg&imgrefurl=http://wiki.talkbass.com/index.php?title%3DFile:Ring_terminal.jpg&h=400&w=400&sz=7&tbnid=K8SsPEKGFXrRBM:&tbnh=92&tbnw=92&zoom=1&usg=__Cwgph3kXNHC914M8YXVsh3fOGcA=&docid=XbWIe9KxSihMVM&sa=X&ei=QJ2TUoTgJ5LroAS5voLgDg&ved=0CG4Q9QEwAg

I only tested 2 units and they typically were taking 550-580 watts on stock settings. I tested it via a P3 Kill a Watt power strip

http://www.p3international.com/products/consumer/p4320.html

Thanks for posting, this led me to balance the load between my psu's. Had one with warm cables, hope swapping some h-boards to another m-board is sufficient.

Thanks for the details AMD - I'm sending this info to the developer and manufacturer - we'll make any necessary design changes immediately.

In the meantime, I hope everyone remembers these are high wattage devices that need special care - keep them away from anything flammable, similar to what AMD has done here.

Stay safe!

Regards
Dave

where's my quote??? :)  hmmm?   ;D



Putting 400-650 watts on 2 x 6 pin PCI-E power cables is risky depending on your power supplies.  Specifically, I learned this with 2 x 8 pin PCI-E cables on a 7990 Malta and Seasonic Gold 850 watt PSU.

Bitfury products are superior...but guys (customers)...please load balance your power and power cables per unit.

After some thinking (and testing) the real fire hazard is not the bitfury. It's that retarded pci-e cable, just use two of them (you got plenty with the pus's) and your good.

[edit] The cable is bad because it's insufiscient for the power needed, note that having two separate cables halves the load on the copper.
[edit2] Apparrently this conclution was allready reached.

One of my rigs is V1 MB based and has been running heavily OC'd (>500GH/s across 16 boards) for months. I noticed yesterday that the white plastic male connectors (minifit jr 6P) were darkening (near the contacts) due to heat damage - fortunately there was no damage to the PSU or PSU cabling. The connectors were hot to the touch, likely due to the current handling capabilities of the pins are being exceeded. I'll upload a pic when I get home

This rig is in my basement which is very, very cool. PSU is a Corsair AX850. No damage has been observed on any connectors (board or cable) either on this rig or my other two. Heatsinks are installed on every HB and 3 HSFs per rig.

I'd advise everyone to check connectors regularly, and to exercise caution when overclocking.

Thanks Jim - I second that emotion!

Folks please power your rigs with two *seperate* cables from the PSU.  Full rigs should probably use a 1000w or great power supply for safety's sake.  Check your rigs often.  This is all stuff we faced back in the GPU mining days :P

I've been GPU mining litecoin/bitcoin for years and have never seen this .. the problem is that you're exceeding the 6-pin's capacity severely. These power cables are only intended to carry 75w each, while 8 pin connectors can carry 150w each.  If you intend to have these running at 600w as the latest rigs have been, you need 4x 8 pin connectors.  Why the designers chose to do something so glaringly out of spec is a mystery to me.

In the meantime, I would suggest that people begin connecting the 12v lines from molex or 6/8 pin adapters directly to the +/- terminals at the other end of the hboard in addition to the 2x 6 pin adapters. My rig is only pulling 390w, but both cables remain warm even at an ambient temp of 4C

We've had this incident once (happened overnight) with a rig that had both cables plugged. How well they were plugged, that's another question. The Molex Mini-Fit Jr is an ok connector and should handle 13A on each circuit (http://www.molex.com/webdocs/datasheets/pdf/en-us/0026013114_PCB_HEADERS.pdf), but sometimes it doesn't connect properly and you get arcing and overheating. And sometimes PSU manufacturer saved by using thinner cable :P

This is PCIe spec, not molex.

Well, each 6 pin has 3x 18 gauge awg 12v + ins, which should hold 10 or 11 amps each in theory. That means a max wattage of 360 - 400w each, but you get pretty close to the max at 600w load. If the psu cheaps out and uses 20 or 22 gauge awg you will probably run into problems.

Or just solder big fat wires directly to the board and the PSU bypassing any connections that might cause you trouble.

Though I doubt that there would be any point in using a overpowered PSU other than efficiency. Any good quality power supply can handle full load (though I would modify them to spin their fans at full speed all the time instead of the "silent" nonsense). If you buy a low quality power supply, it can just blow up (shorting the outlet) because it uses active PFC and the primary cap dies (I have repaired one such PSU and have ordered parts to repair another).

+1

Hi Punin, as I'm sure you know, 13A/pin is dependant on the type (and quality) of the pin used in the housing. I think it's quite possible, even likely, that the contacts used in the PSU adapters are the culprit, at least in my case.

Contacts (e.g. pins) have a current rating as well, which is independent from the capacity of the wire.

Here's a decent chart for current capacities of AWG sizes  ;D

http://www.powerstream.com/Wire_Size.htm

Learn it,live it.......or burn it  :D

Get male connectors from here,add the pins though,not auto included:

6pin:
http://www.frozencpu.com/products/8620/ele-361/FrozenCPU_ConnectRight_6-pin_Male_PCI-Express_Power_Connector_-_Black.html?tl=g51c385s1005

8pin:
http://www.frozencpu.com/products/8693/ele-369/PCI-E_8-pin_Male_Power_Connector_-_Black.html?tl=g51c383s1007

For a heads up, all my rigs use separate 6 pin pci-e power cords. You can see from my pictures that there are 2 psu cords plugged into that XFX 850. I didn't use one cable with 2 6 pin pci-e ends being that would be 550w through 18 ga wire which you'd fry in no time.

It's also a good idea to never load a connector/outlet more than 80% of what its rated for 24/7 use. This can be seen in the US national electric code in numerous areas. It goes into detail in NEC Table 210.21

Ok, i want to say again... I've used seperate PCI-E cables before and yet the plugs on the cables have melted on the inside of my modular power supply.  Yes they were absolutely plugged in tightly..they click in.

With that said Cables CAN still melt even if they are both separately plugged in.  I've had it happen to me on a 7990 Malta before.

My conclusion is not all power supply manufacturers make the same  PCI-E cables and thus they can only take a certain amount of watts / current through them.
For reference this happened on a 7990 malta video card and a Seasonic Gold modular 850 watt supply.

Bad power PCI-E cables CAN cause the melt.

Did anyone notice on the picture of the melted cables that the ones on the top right where a thinner gauge than ones on the bottom.

How thick your wire is (gauge) determines it's the melting point / max load. It should be written on the cable.

The ones with "PSU" look very odd having two different gages and three wire on the top and four on the bottom.

Maybe it's a safety feature to stop it melting into a short, or maybe the manufacturer was cutting corners, I dunno, but the thinest wires are determine the max load on this cable and it's not as good as the cable on the far right with nothing written on it where both the top and bottom wires are the same gauge.

http://en.wikipedia.org/wiki/American_wire_gauge

http://img27.imageshack.us/img27/6854/fkx0.jpg

This happened to me as well. I made the mistake of going from 8pin PCI-E to dual 6 pin on the same modular PSU cable. I now have two separate PCI-E power connectors but I still worry it may cause melting in the future. The system draws 418 watts on average now.

Tip for you guys, make sure if you overclock the boards that you a) run separate PCIe cables from your PSU b) use the thickest gauge PCI-E cables possible c) if possible run an additional 12v to the screw type power connectors on the m-board.

Speaking of which does anyone know where I can buy a pci-e 6 pin (or even molex) to the screw type connectors? (ie plus and negative 12v)

I personally think they should've used 2 x 8 pin PCIe jacks on the m-board. They knew people are going to try to overclock these and thus power consumption would be noticeably higher.

Like you say according to the AWGs they should be able to hold more - but those AWGs allow wire temps up to 80C or something rediculous. That's why 6 pin PCI-Es are rated at 75W [should really be ~150W] and 8 pin at 150W [should really be ~250-300W].

From the ASICMiner blades, I can tell you tough that plenty of things that say they are 18AWG clearly aren't and burn pretty quick.

If I'm using a 700W PSU - could that cause my rig to perform lower than expected?  Should I bump it to a 1000W PSU JUST to utilize higher hashrates?  I'm lucky if I see 460-470 GH/s on 700W coolermaster

Okay...Ive done this (routed to both the screwed connections and also to the two six pin Pcie cabled sets.

DONT OPEN THE PICTURES IN MAINTHREAD! THERE WHERE kid porn! I have report it to an mod.

Where did you get your screw connector from?

Waaat ??? I looked yesterday & today & saw no such thing,assume your PC was compromised already & reinstall your OS ASAP  ;)

The pictures is what's throwing you off. The cable itself is rated at 18 ga @ 90C. There's a lot mentioned in this thread that people don't understand so let me clear some things up. XFX (seasonic design) in there 850w psu line uses an 8 pin plug that plugs into the psu. They only utilize 7 pins of the 8 pin connector, but use 8 wires. The reason for this is a 6 pin and 8 pin PCI express connectors each only use 3 hot wires while the rest are all grounds. So according to pci express specifications, a 6 pin (3 power, 3 grounds) is rated for 75 watts while an 8 pin (3 power, 5 grounds) is rated for 150w watts. So this psu design is based off pci express spec should be able to push 300w through this cable with overhead. If the bitfury unit utilizes all 3 power inputs then you should be fine. Otherwise no matter what psu pushing 300+ possible watts through three 12v power lines is pushing 9 amps through 18 gauge wire and is not a good practice. The 18 ga wire should be fine to push that amperage, but the quality of terminals/connectors whether in the psu or on the wire may not be able to support this.

If the bitfury m board doesn't have the space to accommodate an extra 6 pin power, then it would have been smart to utilize the screw attachment for a 3rd set of power connectors. Oh also you can see the one psu cable melted, but the other cable was on the verge of melting too as the cable is extremely stiff and upon trying to remove the psu cable I eneded up cracking the connector as so much heat was generated it looks to have started melting and was partly fuzed.


PSU Review

http://www.legitreviews.com/xfx-pro-series-850w-black-edition-psu-review_2239/8

http://www.hardwaresecrets.com/article/XFX-PRO-850-W-Black-Edition-Full-Modular-Power-Supply-Review/1716/13


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Right now I am using two seprate 6pin connectors and the total system draw iw 408 to 418 watts at the wall. I am hoping this is safe. The boards are overclocked but only slightly. I could push them higher - and they were - but once again the power draw would melt the wires. I am not sure what solution would work to give the boards more power. I forget if the v2.3 m-board has any screw type power connectors. I know the new style m-boards have both though.

I guess I should mention that I'm powering the rig with a Corsair AX860.