Asrock H81 & Radeon 7990 incompatibility
#1
Hello,

I'm trying to setup a Asrock H81 Pro motherboard with 6x Radeon 7990.

When I have 3x 7990 connected system boots normally. When I connect the 4th 7990 the board reports about 50 short beeps. I asked Asrock but they have never heard about 50 short beeps...

It is not a GPU issue as I have tested them individually and it is not a PCIe slot issue. If I have any 3 GPUs it works great, when I connect the 4th, the system won't boot.

Setup:
- Asrock H81 Pro board with Xeon E3, 8GB RAM
- 2 Corsair 1200w PSUs
- 6x Radeon 7990 (3 Gigabyte and 2 XFX)
- 6x Asrock BTC Kit risers
- One PSU is connected to motherboard (including 2x MOLEX) and 2x 7990
- Other PSU is connected to 4x 7990

Thanks a million!

Mike
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#2
There is some GPU limit, 8 to be exact for AMD. Your motherboard already have one integrated, so if you connect 4th 2GPU card, you in total having 9 GPU on your system. So first of all you should disable integrated gpu and try booting.
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#3
the short beeps are likely related to 32-bit PCIe addressing. see if your bios has an option called "Above 4G Decoding" and if so, enable it. if it doesn't, then your board is not capable of 64-bit PCIe addressing.

once you get past that though, 6x 7990 will still not work as the driver only supports a maximum of 8 GPUs. most you can do on one board is 4x 7990.
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#4
>So first of all you should disable integrated gpu and try booting

There is no option to explicitly disable internal GPU (its actually the GPU in the CPU). There is an option to choose either the internal GPU or the PCI GPU. When I change to the PCI GPU when I boot with 4 cards I no longer hear the 50 short beeps, but the system won't boot (there is no BIOS screen). If I install the 5th GPU I will hear the 50 beeps again.

So it seems to be related to the number of GPUs. Is anyone using this board with a GPU bultin the CPU?

>see if your bios has an option called "Above 4G Decoding"

No it doesn't

>There is some GPU limit, 8 to be exact for AMD

isn't the 8 GPU limit a Windows issue? If its a Windows issue it should boot into Windows and then the additional cards not be recognized right?
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#5
No, it's not a Windows issue, it's an AMD driver issue.
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#6
> No, it's not a Windows issue, it's an AMD driver issue.

Just to clarify, when you say driver you mean Windows driver right? So the system should at least boot to BIOS right?
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#7
You're not really paying attention to what has been said.

Your BIOS does not have the "Above 4G decoding" option, and therefore does not support 64-bit PCI-e addressing. That's why you're not able to POST.

IF it did though, it still wouldn't work because the AMD driver does not support more than 8 GPUs.

So no matter what you do, your plan will not work.
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#8
Now I understand, thanks.

I'll double check with Asrock to see if there's any way to enable 64bit addressing because this company was selling mining rigs based on the Asrock H81 Pro with 6 Radeon 7950 connected to each board:

http://www.ocaholic.ch/modules/news/arti...1481237582
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#9
7950 is a single GPU card. 7990 is a dual GPU card. Each 7990 counts as two GPUs. So you're trying to connect 12 GPUs to the board.
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#10
Quick update: I opened a support case at Asrock, they supplied a beta BIOS update with 4G Decoding, but the problem remains the same:

- If the onboard graphics is disabled, I can boot with 3 GPUs
- If the onboard graphics is disabled, I cannot boot with 4 GPUs – blank screen, does not POST
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