I have just built a CYCLES GPU rendering beast from second hand 5xx graphic cards.
580 is primary card, plus two 590 cards. When I hit render on the scene, it uses only
4 GPUs instead of 5, four tiles appearing during render. User preferences shows all
of them [580+590(4)]
When I remove the 580, I have same rendering times
Why ?? are there any limitations to 4GPU ? or 2 PCIe slots?
any help will be appreciated
with friendly regards
Jozef
PS: it is rendering Mike Pans BMW test 256x256 tile size in 19s 74ms
The GTX 590s are internally running with SLI. Did you disable it in the drivers? You have to set the “Multi-GPU configuration” to “Disable multi-GPU mode” for the GTX 590s.
PCI-E speeds should not provide any problems. Even the slowest PCI-E slot will do the job really good as you are not playing games, ie not streaming information in real time. There was a test some guy did awhile ago where he tested acient mobos with todays cards and it practically didn`t suffer any speed losses.
I can aprove this, i have tested it too. I have an 5 years old MSI P7N Diamond http://www.msi.com/product/mb/P7N-Diamond.html#?div=Detail with famous NVIDIA® nForce 780i SLI+570i SLI chipset. It also supports 3-way SLI, but I am not using it, because of GPU computing. It can handle everything very well still in these days.
I repeat, try to change the order of gpus. Primary card has to be in the first 2.0 16x slot (anyway read the motherboard manual). Maybe 590 in primary slot can give problems. If it doesn’t work, you can disable 580 as cuda device and see again how two 590 work.
