5 GPU problem (MB: GA-990FXA-UD5)

[callawey]

i am using GIGABYTE GA-990FXA-UD5 V3

I have 2x Sapphire HD7990 & 3x Gigabyte R9 290
All my risers are 4x to 16x with powered molex. I tried combinations on the slots by swithing gpu's but what ever i do, system doesnt sees the 5. gpu not even as error, its like 5. one isnt connected to any pci slots. I didnt tried 1x pci slot because i dont have 1x to 16x and i am not sure will it work or not if i get 1x to 16x. But i see people that are using this MB with 6 gpu's.

Operating system is 8.1 but as i said this isnt about the os (maybe i am wrong) because there is no 5. item as error on the system its like its not plugged.

If any one faces a issue like this and solved it, please let me know what did you done to make it run ?

[ckomega]

i also meet this problem,

on motherboard, four GPUs is ok, but the fifth GPU can not be recognized in system.

i am using BIOSTAR Hi-Fi H81S2 motherboard, five R9 280x , 12G ram.

if you have any solution, please tell me?

thanks

[matt4054]

I'm afraid the answer is that the Windows HAL will not recognize more than 4 GPUs (categorized as display device) on any system.

So the culprit would be the OS, not the hardware. If that is the case, I would suggest a Linux-based rig instead.

EDIT: more info in this old post that I just Google-digged.

[callawey]

i found the problem for this mobo, if you are using 4x gpu with 4x to 16x, then you can add fifth one only by using the 1x pci with 1x to 16x, this way you can have 5gpu, if you want 6gpu, you have to use 1x to 16x on all of the pci slots, if you are using 4x to 16x, than you can only use four of the 5 16x pci slots.

As it seems if you use the slots by 4x to 16x, bandwith isnt enough for pci slots but with 1x to 16x all worked

[Namun]

i found the problem for this mobo, if you are using 4x gpu with 4x to 16x, then you can add fifth one only by using the 1x pci with 1x to 16x, this way you can have 5gpu, if you want 6gpu, you have to use 1x to 16x on all of the pci slots, if you are using 4x to 16x, than you can only use four of the 5 16x pci slots.

As it seems if you use the slots by 4x to 16x, bandwith isnt enough for pci slots but with 1x to 16x all worked

I`m having the same problem, with the same board GA-990FXA-UD5

I've got 6 GPUs connected (2x 280x, 1x 290, 2x 290x) using 1x to 16x unpowered risers everywhere, and only 5 GPUs are visible (using Windows 8.1).

Also I`m using 3 PSUs x 750W and since 4 cards work properly with 2x PSU (getting the maximum possible hash rate per card I suppose this isn't the problem).

Did I miss anything ?

EDIT: It seems the one from the 8x slot is not shown.