Bitcoin Forum

A lot of us have read that Windows has a 4 GPU limit and that Windows XP can't do 4 GPU's.  Let's verify/dispel those myths.

• Is there anyone out there that has more than 4 GPU's mining on a box running Windows OS?
• Is there anyone that's been able to get 2, 3 or 4 cards mining using Windows XP?

Edit: If anyone can answer yes to either of those above, please list your hardware/software setup.

Yes, I have had 3 6970's running on XP.  However, I had heat issues and had to remove one to another box.  I used the Guiminer, poclbm, 2.4 drivers, (and cat 11.4  I think, not sure).  MB was a ASUS Crosshair IV Formula.

I'm running 3 x HD5870 on Windows XP with an Intel DX975XBX motherboard and an Intel E6400 with 1 GB DDR2. I'm using single resistor dummy plugs in cards 2 and 3 and all 3 cards are running at 950/300. I run 2 Phoenix instances on each GPU with identical settings, so I cover 2 pools in case one has problems. My total hash rate is just over 1,200 MH/s.

Not an XP/Windows problem, but to get around the heat issue, as the cards are so close together, I use insulating spacers to push the cards apart and I've cut holes in the case and fitted 2 fans that blow air directly onto the middle card.

I have 4 card on XP right now.  2 5850's, 1 5870, and 1 6870.  I don't OC them much and I get about 1.2Ghash.

So it looks like up to 4 cards in XP is fine.

What about 5 or more cards running in Windows, anyone been able to make that work?

5 cards and up wont work due to a limitation in windows, they simply wont be recognized by the operating system.

Not true.

I had 5 cards working under Windows for about 2 days. I don't currently as I rearranged to load balance, but with Dummy Plugs I had no issues.

Cable, which cards, mobo and OS were you using?

Win 7 Ultimate x64
Gigabyte EP45-UD3P motherboard, all cards run through extender. 2 x16, 3 x1->x16.
Ran 1 5970 (Sapphire), 2 5870 (XFX), 1 5830 (Sapphire.)

but that's only 4.
1 + 2 + 1 = 4

5 GPU though... So Windows still somewhat had to handle 5 GPUs... now it depends on what the drivers showed windows, but it is technically 5 GPU...

Hmm, yeah, the 5970 is dual GPU, so it could be that it only works with 5 cards or Cable was only using 4 GPU's (1 off the 5970).  Cable, were you using all 5?

Is there anyone out there that's gotten windows working with more than 4 physical cards?

Has anyone tried running 5 with virtual machines? I do not know enough about them to know if it would work but could you assign 3 to one machine and 2 to another?  I am very curious...have another 2 cards on the way and I would rather run 5 per machine...pretty sure I can pull it off physically with card extenders.

Remember AMD APP SDK support for Windows XP stops at v2.4 :)

Can you post your speeds per card?

That's the only way of verifying whether you have all 5 GPUs working.

Someone from this thread confirmed that you cannot mine with more than 4 GPUs:
http://forum.bitcoin.org/index.php?topic=19038.0 (http://forum.bitcoin.org/index.php?topic=19038.0)

Windows showed 7 GPUs detected for this computer, but that's meaningless, since openCL drivers only support up to 4.

There are no myths here...

On windows, prior to driver 11.6 only 4 GPUs would work.

GPU does not equal a video card in this context...
Windows will recognize more than 4 video cards just fine... However, you won't be able to use more than 4 GPUs with 11.5 or below.

However, with 11.6 drivers, it looks like there's limited confirmation of 8 GPUs being the new limit.
On Linux there are rumors that the limit is at least 10 GPUs...

XP support at least 4GPUs
7 supports at least 8GPUs, but only 4 can run OpenCL.

With the new 10.6 drivers, the limit on Windows is now 8 OpenCL

Hmm, that's awesome.  Of course, you run into power requirement issues with that many cards, but it's nice to be able to bundle things up into fewer machines.

So, that leads to the question of what are some good suggestions for motherboards that have 5+ PCI express slots?

I'm running an ASUS WS Revolution with 7 GPUs with Windows 7, AMD currently has a ticket from me escalated to engineer to deal with the need for dummy plugs with 11.6.

If AMD gets rid of the dummy plug for win, that will be SUPER fantastic!!!!!
Please keep us posted!

Nice.  What GPU's/PSU are you using?  My main concern with 5+ cards isn't really the overall power needs of the cards, it's that I believe the cards can draw 75W through the PCI express slots.  7-8 cards is 600 watts pumping through the board just for the GPU's and I wonder if that would be any cause for concern?

Guys please help me here! I cant get to work with 3 cards (5 GPU) and this is my four day with the problem and still no solution :(

http://forum.bitcoin.org/index.php?topic=21687.0

I tried to mine with 8 GPU's in Linux - Ubuntu 11.04. Mother board is MSI big bang Marshal. The problem is not Linux but PSU.
I can mine with 8 cards , if don't over clock, don't have any fans installed....
To cool GPU's i use 120 mm fans, 6- 8 fans & PSU can't able to give power with 8 cards + fans.
I used 2 PSU's & i still can't believe the PSU sucked.
Cooler Master Silent Pro Gold 1200 W. Before buying i wrote to cooler master & got confirmation that it will support 8 GPU's.
Yes it supports 8 GPU's in Ubuntu, but mining & adding fans makes the PSU to go off.
Then i used another PSU, 3, 1200 W to mine with 8 cards, but due to not able to under clock memory of 6970's heat went up to 95C+ , so stopped using that.
My advice, unless you know how to cool, avoid more than 6 GPU's.
Also Cooler Master even though having 80 gold certificate sucks, seems they got fraud certificate or something & also in AMD's certified PSU's only 2 nos of 5870 is mentioned as CMSPG 1200w supports.

If you want more power, yesterday found out, silverstone ST-1500W can able to with stand 4 GPU's , I emailed them & they confirmed.
Still cooler master gave me failure , i can't trust it now. But 1500W can support, i hope.
My system had 5 nos. of 5870's (2 ASUS EAH 5870, 1 Sapphire HD 5870, 2 MSI R5870 Lightning) & 3 nos. of MSI R6970 Lightning.

Well, I know for a fact Windows XP doesn't have a hard 4 GPU limit.  I used to run Folding@Home on 4 9800GX2 video cards, so 8 GPUs, on Windows XP x64.  If there is an issue, it's manufacturer specific then.



Well duh, of course a single 1200W power supply isn't going to be able to handle the load of 8 GPUs.  You get a max of 98A @ 12V, so 1176W to work with on the 12V line.  Figure your system probably has around 100W overhead, so you're down to 1076W to split among 8 video cards, or 134W each.  Unless you're using some pretty low performance video cards, you're overloading the power supply.  You're probably going to have to run a second power supply to power at least a couple of those cards.

Before answering, READ what said.

He used up to 3 power supplies, not one.