Building a multi GPU system

[eleuthria]

When building a computer specifically for mining BitCoins, with ATI/AMD cards, is it neccessary to match the cards up like you would in a gaming machine, or can I simply plug in whatever card I have available at the time?

Right now I have a 6990 on the way, and I already have a 5970.  Can I just plug in those two cards without any special setup?  Additionally, could I add a 5870 to the mix as long as the motherboard / PSU can support all 3?

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[Garrett Burgwardt]

Doesn't have to be matched, but thermals will be a problem with those two cards.

[FoS]

I have also a question about that. I have a 5850 and a 5770 in a mobo Asus m2n-e sli. It has 2 pci-e slots so I can plug both cards but when I use the miner it only shows me the first one and in GPU-Z only the card that is in the primary slot has OPENCL. There is some way to use both to miner? At least I will have to use only 5850 but it would be great if I could use both.

[eleuthria]

Doesn't have to be matched, but thermals will be a problem with those two cards.

Yeah, I'm interested in seeing the temperature interaction between the two cards.  I'm using a Cooler Master HAF 932 for the rig, which in my experience with gaming rigs is able to very easily run multiple hot GPUs without much issue.

[TenthReality]

I have also a question about that. I have a 5850 and a 5770 in a mobo Asus m2n-e sli. It has 2 pci-e slots so I can plug both cards but when I use the miner it only shows me the first one and in GPU-Z only the card that is in the primary slot has OPENCL. There is some way to use both to miner? At least I will have to use only 5850 but it would be great if I could use both.

Do you have a monitor plugged into it?  If not, plug one in.  Stupid quirk of the system requires it to have a monitor.  If you lack a 2nd monitor you can search around on how to create a DVI->VGA null monitor adaptor (takes 3 75ohm resistors from radio shack to make it happen).

[mrjones]

Right now I have a 6990 on the way, and I already have a 5970.  Can I just plug in those two cards without any special setup?

I've got that exact configuration and it doesn't work at all I'm afraid.  At least not with 64-bit Windows 7 and Catalyst 11.3 or Catalyst 11.4 (beta), and the 2.4 Stream SDK.

What happens is that if you have both cards enabled in Windows (i.e. with monitors connected, and your desktop expanded onto them), any OpenCL program you try to launch will simply freeze when it tries to initialize the OpenCL subsystem.

If you disable the 5970, then you are able to start OpenCL programs but they can only see the 6990.  AMD says they know about the problem and are "looking into it" but I'm not hopeful for a resolution anytime soon.

The 6990 is also frankly a bit annoying for everyday use, because if a program is using the first GPU for OpenCL calculations and you watch a video (YouTube, Windows Media Player, etc.) the video driver freezes and you have to reboot. This is also a "known issue," although I'm more hopeful for this one to be fixed.

But as far as the two cards working together ... I wouldn't hold out hope.  If you can figure out a way to make it work, I'd love to know how you did it.  :-)

[Meni Rosenfeld]

If it's a machine just for mining, put Linux on it. It handles multi-card configurations much better. There are guides available.

[FoS]

I have also a question about that. I have a 5850 and a 5770 in a mobo Asus m2n-e sli. It has 2 pci-e slots so I can plug both cards but when I use the miner it only shows me the first one and in GPU-Z only the card that is in the primary slot has OPENCL. There is some way to use both to miner? At least I will have to use only 5850 but it would be great if I could use both.

Do you have a monitor plugged into it?  If not, plug one in.  Stupid quirk of the system requires it to have a monitor.  If you lack a 2nd monitor you can search around on how to create a DVI->VGA null monitor adaptor (takes 3 75ohm resistors from radio shack to make it happen).

Ok thanks, do you know if dvi-vga adaptor that comes with the graphic card would do the same use?

[TenthReality]

I have also a question about that. I have a 5850 and a 5770 in a mobo Asus m2n-e sli. It has 2 pci-e slots so I can plug both cards but when I use the miner it only shows me the first one and in GPU-Z only the card that is in the primary slot has OPENCL. There is some way to use both to miner? At least I will have to use only 5850 but it would be great if I could use both.

Do you have a monitor plugged into it?  If not, plug one in.  Stupid quirk of the system requires it to have a monitor.  If you lack a 2nd monitor you can search around on how to create a DVI->VGA null monitor adaptor (takes 3 75ohm resistors from radio shack to make it happen).

Ok thanks, do you know if dvi-vga adaptor that comes with the graphic card would do the same use?

No, you need to modify the one that comes with the PC.  Follow this guide: http://www.overclock.net/folding-home-guides-tutorials/384733-30-second-dummy-plug.html

But based on other folks replies here, it seems like this is just going to expose the next problem you're going to have.

[mrjones]

If it's a machine just for mining, put Linux on it. It handles multi-card configurations much better. There are guides available.

The 6990 is not supported under Linux yet, even with the 11.4b hotfix.

Probably will be fairly soon; all other 6900 series cards are.

[FoS]

Ok, thanks TenthReality, tomorrow I will go to buy some resistors and I will try that.

[mrjones]

... this is just going to expose the next problem you're going to have.

Damn, I should have that printed on a T-shirt after my 6990 upgrade fiasco.   

[eleuthria]

So since the 6990 might not be ready for full duty mining yet, should I swap my 5970 (currently in my gaming rig) with the 6990, and then plug in the 5970 and 5870 into my mining rig?

[mrjones]

So since the 6990 might not be ready for full duty mining yet, should I swap my 5970 (currently in my gaming rig) with the 6990, and then plug in the 5970 and 5870 into my mining rig?

If you're using the 6990 by itself, it will work fine for mining.  I'd leave the 5970 in your gaming rig (and do bitcoin mining in the background) since it won't lock up your system while mining if you watch a YouTube video, etc., like the 6990 will.

[eleuthria]

Alright, so it looks like the best way to utilize the 3 cards would be:

Mining Rig: 6990
Gaming Rig: 5970 mining when not in use.  5870 added to system, and mining 24/7.

[mrjones]

Alright, so it looks like the best way to utilize the 3 cards would be:

Mining Rig: 6990
Gaming Rig: 5970 mining when not in use.  5870 added to system, and mining 24/7.

Sounds perfect. The current drivers will also be very happy with that configuration.

[allinvain]

So since the 6990 might not be ready for full duty mining yet, should I swap my 5970 (currently in my gaming rig) with the 6990, and then plug in the 5970 and 5870 into my mining rig?

If you're using the 6990 by itself, it will work fine for mining.  I'd leave the 5970 in your gaming rig (and do bitcoin mining in the background) since it won't lock up your system while mining if you watch a YouTube video, etc., like the 6990 will.

Wow what a stupid bug to have. Does this happen with every Catalyst drivers package of only with certain ones? Also have you tried disabling GPU acceleration in flash? I heard that can cause the video card drivers to lock up. Also update flash to the latest version.

[mrjones]

Wow what a stupid bug to have. Does this happen with every Catalyst drivers package of only with certain ones? Also have you tried disabling GPU acceleration in flash? I heard that can cause the video card drivers to lock up. Also update flash to the latest version.

It seems to be every driver version, and GPU acceleration in Flash makes no difference (tried both ways).  But it's not Flash-related--it's a problem with any video overlay. There's the same problem playing video in any other applications (Windows Media Player, Media Player Classic, etc.).

See this thread on the Bitcoin Forum where it has been discussed extensively, along with the official "GPU lockup if running OpenCL and playing video at the same time" thread on the AMD OpenCL forum.  It was a problem a year ago with different cards and different drivers, and then resurfaced again now with the 6900 series.

[allinvain]

Wow what a stupid bug to have. Does this happen with every Catalyst drivers package of only with certain ones? Also have you tried disabling GPU acceleration in flash? I heard that can cause the video card drivers to lock up. Also update flash to the latest version.

It seems to be every driver version, and GPU acceleration in Flash makes no difference (tried both ways).  But it's not Flash-related--it's a problem with any video overlay. There's the same problem playing video in any other applications (Windows Media Player, Media Player Classic, etc.).

See this thread on the Bitcoin Forum where it has been discussed extensively, along with the official "GPU lockup if running OpenCL and playing video at the same time" thread on the AMD OpenCL forum.  It was a problem a year ago with different cards and different drivers, and then resurfaced again now with the 6900 series.

Hmm, interesting. I did run across that AMD thread when I ran into a similar problem with my 5970. The system blue screened while I was trying to load a youtube video from within facebook. At the time I was running 11.2. What I did was run driver cleaner and install 11.3 after and update flash, turn off gpu acceleration - so far no crashes. Not sure if it was 11.3 that fixed it or what, but I do think this problem can happen with 5970 too. Has anyone else had this with the 5970 or am I the only one? (win 7 64)

[mrjones]

Hmm, interesting. I did run across that AMD thread when I ran into a similar problem with my 5970. The system blue screened while I was trying to load a youtube video from within facebook. At the time I was running 11.2. What I did was run driver cleaner and install 11.3 after and update flash, turn off gpu acceleration - so far no crashes. Not sure if it was 11.3 that fixed it or what, but I do think this problem can happen with 5970 too. Has anyone else had this with the 5970 or am I the only one? (win 7 64)

I was using a 5970 until I got this 6990 on Monday, and I upgraded my drivers every month, through 11.3, on Win 7 64.  No crashes.  The only problem I had (which started long ago) was that with GPU acceleration turned on in Flash, the image on my second monitor would jump up momentarily when a video started (actually not the entire image; there would be a black bar about 1/4 of the way up the screen about 50 pixels tall, and the image above that bar would jump up and back down).  Other people had the same problem.  I simply turned off GPU acceleration months ago and forgot about it.  

Edit: The 6990 does not have that problem, which is nice.