Running 5 GPU on Gigabyte 990 UD3

[cjw3211]

Hi there, I wondered if anyone here has better brains than me and can solve this?

I have a Gigabyte 990XA-UD3 board.

It has in this order starting from CPU:
1_PCI x1
2_PCI x16
3_PCI x1
4_PCI x16
5_PCI x16

Now with 3 cards plugged directly into board in the 3 x 16 slots all 3 are detected and work fine.
So cards in 2, 4 and 5 is OK.

With cards in risers, the card in the second (middle) x16 slot isn't detected. I have 5 cards plugged in but Win 8 only sees 4.
So cards in 1, 2, 3, 4 and 5 all with 1x PCI express risers (powered) card 4 doesn't get detected at all. It does this whether or not slots 1 and 3 are shorted on pins A1/B17 to do the presence mod.

Some people suggest shorting the pins on the x16 slots exactly the same way - so I have tried to short out pins A1 and B17 on the x16 slot, but with them shorted the mobo won't turn on. That goes for if I short out sockets 2 or 4. As soon as the shorting wire is pulled out the power comes on.

What's the trick to getting the BIOS to detect this card?

I have also tried this exact same thing on a cheap Gigabyte Ga-Z68 board and it does detect all 5 cards in windows with the same powered risers. The reason I have changed board is that the cheap board isn't stable when mining Litecoins.

If anyone solves this for me I will pay a bounty in LTC or BTC.

 

[tachybana]

Unless i have the wrong board, it says only 2 way Crossfire is supported with this board (only the GA 990FXA UD7 supports 4 Crossfire)

 

[cjw3211]

Possibly, but it does take 4 GPUs, and a cheaper Gigabyte board will take all 5 quite happily.

 

[cjw3211]

I may have actually just solved this myself. Put the card in the 8x (middle x16) slot on a 16x riser and it works.

Don't understand why though....and why I can't use a 1x riser....

 

[tachybana]

Glad it turned out well