Quote from: sunbreak on March 14, 2014, 04:28:47 AM

Quote from: sidehack on March 12, 2014, 01:42:29 AM

Preemptive disclaimer that I don't work with GPUs a lot.

But I would imagine the 300W and 280W from your cards, part of that is coming from the risers. If you don't plug the risers into a heavy external supply but run them off your ATX, I'd allot at least 6A of 12V per riser. If the 300W/280W is straight external, they should all run off the DPS-1520 without issue. If that includes the socket power (from risers in this case), you could power the risers off the DPS-1520 and still only be at 80% capacity.

If, then, you ran your 6950 and motherboard off the ATX supply, I'd recommend probably at least a 500W unit. Maybe more depending on what processor/motherboard you're running, and what overhead you want to allow for.

What you could do, and an idea I've toyed around with but haven't tested yet, is actually get two server supplies in parallel load-balanced (I don't know enough about that particular model to know if they current-share or not, but I think most do) and get a picoPSU running off the 12V bus for your motherboard. Those things aren't terribly expensive, and run around 96% efficient. If you isolate your riser power from the motherboard power (either by using the recommended USB-style risers or cutting the 12V lines to the ribbon) you shouldn't overload anything on the picoPSU by trying to pull GPU current through it, and anything else requiring 12V (like GPU, or processor VRMs) would pull straight from your ~3KW 12V source.

You mean like this; This is 3 systems all connected to the same DPS-2000BB power supply. Each system has 6 x PowerColor 6950's (some unlocked) for a total of 18 GPU's. This was an undervolted setup with the memory downclocked to 150mhz through a bios mod. So overall power consumption per system was about 750 watts. The IBM PSU if properly cooled will do 200 amps before OCP trips. So you can actually get upwards of 2300+ watts reliably.

http://imagize[Suspicious link removed]ageshack.us/v2/1024x768q90/99/imag0094q.jpg

A previous client and I had these picopsu like boards made in china in bulk. They are a special design, unlike a normal picopsu that regulates the 12V line and limits it's current. This design passes the 12 volt straight through without regulation and provides a full 10 amps on 5v and another 10 amps on 3.3v. The connector and wire gauges are sized so that the current from the 3.3v and 5v do no impact the overall current available on the 2 x 12 volt atx pins. Also the CPU connector is straight pass thru. The connector was spec'd so that I could be put on powered from a standard ATX PSU from the 8 pin CPU header (only 4 pin CPU pass thru). Since most PSU's have two 8 pins (one dual 4 pin) you could power two individual systems and then yet one more from the ATX PSU's monster 24 pin cable. However it's very difficult to have enough power to power 3 systems on a ATX PSU as most are limited to 1200-1300 watts.

http://imagize[Suspicious link removed]ageshack.us/v2/1024x768q90/441/imag0091zf.jpg

This is a break out board. So the PSU powers each system with a single pair of #6 copper wire. Then this break out board gives you all the pig tails in addition to the 8 pin CPU style connector to power the motherboard.

http://imagize[Suspicious link removed]ageshack.us/v2/1024x768q90/33/imag0089t.jpg

A closer look at the PSU adapter break out I made.

http://imagize[Suspicious link removed]ageshack.us/v2/1024x768q90/829/imag0088cn.jpg

Where did you buy the power cables and Y-splitters for the GPUs??