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. :/

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.

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

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.