Fun with GPU's

[Terry1953]

My son Ryan and I found out today that Crossfireing 2 6870's with only a 750 watt power supply is a bad idea. It was up and running like a house on fire until I noticed that the temps on the gpu's were 61c and 84c I shut windows down and asked Ryan to pull the power cable out of the back of the machine so I could pull the hot gpu and I was going to clean it and put some arctic silver 5 on the cpu. When he grabbed the power cable running from the wall socket to the power supply it was so hot it left a mark on his hand! The second gpu wasn't pulling the power it needed and was in the process of frying the whole setup. So we're just going to scatter them over various machines and not order any more. They sure do suck the power.

[Dirk Broer]

AMD claims it can be done with as little as a 600 Watt PSU

[AMDave]

Yes it can be done, for the sporadic load while gaming, but not for 100% load GPGPU crunching, I think.
But then again, it says so right there on the page you linked to so you'd think they'd have stress tested it.

[vaughan]

Thanks for that insight Terry1953. Does that mean its OK with a higher rated power supply, say a 1200W or is it still going to be a fire hazard when we crunch BOINC 24/7?

[Dirk Broer]

I would not want to rely on the stock coolers when crunching on a duo of HD 6870s, but either place two of these:

or use water cooling

[Terry1953]

Dirk I think the cooling was fine because the problem child is happily crunching away at 68c in it's own private box. When I checked the wires it was only the ones leading to the 2nd gpu that were hot and the first one was running well under any problem temp. The EVO board we had it on has 3 16x slots and we had them spaced in slots 1 and 3 with fans everywhere. There were 2 120mm exhaust in the top, 1 120mm exhaust at the rear top , 2 120mm blowing on the face of the mobo.1 120mm blowing in from the front. 1 120 blowing in from the bottom right on the face of the 6870 and a bottom rear mounted power supply with a 120mm out the back and a bottom intake. The problem wire was the lack of a 4th 6 pin power cord and having to use an adapter of 2 IED 4 prong power plugs into a 6 prong. The PS only had 3 6 prongs standard and I guess they figured no moron would want more than that anyway. It was the first time that I ever used every plug on a power supply between the discs, board, cards, and fans. I think I'll just avoid anything that requires 2 6 prong power inputs when I want to crossfire. But it did go gangbusters for the 5 minutes or so we let it run. lol And Vaughn I thought about that and I really do think that a 1000 or 1200 watt PS might be the answer. I think Dave's right about the no 100% 24/7. I think it was just the overload that caused the heat just like to many things on an outlet will heat up the cords and cause a fire. Or if you remember the old fuse boxes (pre circut breakers) that you could bypass a bad fuse by putting a penny in and holding it there with a blown fuse to complete a bad or over loaded circuit. Oh well off to the garage, today we are putting in a new transmission and front and rear air lockers on the Jeep so it's ready to 4 wheel next weekend.

[Dirk Broer]

This might be a handy tool to establish how much power you might need for your rig.
Antec and Corsair PSUs are just rebranded Seasonic PSUs, aren't they?
The Artic Accelerator I placed is meant to replace the stock coolers on your video cards. They -Artic- seem pretty confident in bringing your temperatures down.
They also have models with one or two fans, for smaller cards.

BTW: Terry, did you place te 2nd HD 6870 in the white or in the black PCIe slot? For Crossfire the white slot will give 2xPCIe-8, while the black slot will give PCIe-16 and PCIe-4
ASUS recommends using the Blue and White slots for CrossfireX

[Terry1953]

Thanks Dirk that is a handy tool. It says for that config 850W and up. I can testify that it will take at least that much. I had another 750w overnighted and am setting it up in the 3800+ box now. I moved the 6670 to an old single core intel box that I had running Prime Grid. I should have everything running shortly.

Update LMAO the $125 750w power supply that I paid $3.99 in addition to the Amazon Prime shipping so that I would get it today (Overnight) instead of on Monday arrived DOA. So now I have to RMA the dang thing. I never had a DOA power supply before. I can't believe that they don't test at least the 20+4 pin plugs.

[Brucifer]

Oh well off to the garage, today we are putting in a new transmission and front and rear air lockers on the Jeep so it's ready to 4 wheel next weekend.

I've been running Detroit True Trac's in my wrangler for several years now. Some day when I get rich I'll proly do the air locker thing on the old cj5.

On topic (lol), I've got a 6870 but I hardly ever use it as the heat output is pretty intense, and it helps that power meter wheel spin around pretty good! :-)

[Terry1953]

LOL Yea with 3 6870's and 1 6850 running the little wheel is spinning like an Olympic ice skater. On the even funner topic we put in ARB lockers front and back because we're gettin it ready to sell. we run Duratrac's 37X12.50X16 on Dana 44's front and rear. The onboard compresser is a big plus for airing up for the trip home. We have an offroad park 15 minutes away with 2500 acres. If we were going to keep it we were going to install an 8.8 in the rear but with Ryan going off to college in a couple of months we decided to sell it and build some crunchers since we can crunch even being in two different locations. I'll have most of the machines here the first year as he has to live in the dorm. But the second year he'll get an apartment and he can keep half of them.