I am using an ALTRAD8UD-1L2 (Ampere Altra) motherboard and installing two NVIDIA RTX A3000 GPUs. However, the system only detects one GPU. The second GPU fails during PCIe resource allocation and shows the following errors in dmesg:
pci bridge window [io size 0x1000]: can't assign; no space
pci ... failed to assign
This looks like a PCIe BAR/MMIO allocation issue, but I am not sure whether it is caused by BIOS settings, the firmware on this board, or a hardware/MMIO limitation of the platform.
Could anyone familiar with Ampere Altra or this specific board provide guidance on:
Whether any BIOS options are required (Above 4G Decoding, 64-bit MMIO, etc.)
Whether ALTRAD8UD-1L2 has known MMIO limitations for multiple GPUs
Whether a particular BIOS or firmware version resolves this PCIe BAR allocation issue
Recommend you play around with different slot/card arrangements and let us know what works. The pcie controller is buggy. You may very well be the first person to try this particular combination of cards. I have encountered weird errors as well that were solved by rearranging which cards are in which slots.
If you don’t have a Max CPU, your slots 6 and 7 that you are using for the GPUs are also limited to x8 PCIe
Thanks for the insight. I wasn’t aware that this specific combination might be the issue. I’ll try rearranging the cards in different slots to see if that solves the bugs and will report back with the results.
Which Altra CPU are you using? Your board with Qxx-xx is 2x 16 + 2x 8 PCIe. With Mxx-xx it is 4x 16 PCIe. Not promising this solves but is a good idea to use latest firmware 3.06 if you haven’t already updated it. Is hidden away in the “beta zone” section on ASRock Rack’s page https://www.asrockrack.com/general/productdetail.asp?Model=ALTRAD8UD-1L2T#Download
Problem solved! It really was a game of ‘lucky slot puzzle’ lol.
I realized that slots 4 and 5 are the x16 ones. I previously had the cards in slots 6 and 7, which was why they weren’t being detected. Swapped them to 4 and 5, and everything is working perfectly now. Thanks for the advices guys.
