Four 5850's on GA-990fxa-UD5 How???

[flatronw]

Can anybody please tell me how to get more than 3 GPU cards to work on a Gigabyte GA-990FXA-UD5. I have two identical setups both with the same problem that has given me shit for months.

GA-990FXA-UD5
AMD X2-260 CPU
4 GB Ram 1333
Corsair 1200 w PSU
&
5850 GPU x 8  (4 for each board)

Using:- CGMiner 2.3.2 , 11.6 Drivers and SDK 2.4 on Xubuntu 11.04 64b. This is a full install on a HDD. According to everything I have read, that setup should go well,

but not so!!

Both boards can run 3 x 5850‘s straight off the slots ie PCIE x16_1 ,  PCIE x 16_2  &   PCIE x 8.
By substitution I know that all the cards and the extender cables work properly. The interesting thing is that if you plug the cards into those slots used previously direct, but now using the Extender cables the board will only see the card in PCIE x16_1 It will not recognise the cards in PCIE x 16_2  &  PCIE x 8 with the extender cables. It will however recognise the the second two of the cards if the extenders are plugged to PCIE x 4 _1 & PCIE x 4 _2. Thus giving again a total of 3 cards recognised.
I have done (ad infinitum) the “sudo aticonfig --initial --adapter=all” with all sorts of variations on the -f. and a few of the Fxxck but it does not make any difference.
To me as a Linux and AMD noob it looks like an issue of Latency with the PCIE slots. I have looked thru the Bios (current F8) and cannot see any way to adjust PCIE latency although I have seen references in other posts to figures like “64 adjusted up to 96“ but nothing specific.
Or is it simply that these motherboards will only allow PCIE 3 slots at any one time?

Has anybody had success with 4 or more cards on the GA-990FXA-UD5 or have I bought two pieces of junk?

The only thing that has worked thru all this is Clonezilla, what a Godsend to image discs


Edit:- the extender cables are 16 x 16 with Molex power

Edit:- 13th June, tested with four 1 x 16 powered extenders on all slots, still not able to get FLRGX to see more than 3 cards no matter what!!

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[1714128840]

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[crazyates]

Here are a few suggestions:

Disable everything you don't need in the BIOS. 2nd SATA controller, audio, LAN(?), USB(?), as much as you can.

Are you using x1 -> x16 cables or x16 -> x16 cables? I've heard of people having better luck with powered x1 -> x16 risers.

Update to 11.12, SDK 2.5, and CGMiner 2.4.2.

[-ck]

It's not that hard to reach the bandwidth limits of PCIE slots with lots of GPUs. Open up your bios and see if there's a PCIE latency option. It's usually set to 64. Try increasing it to 96 or 128; it won't have any effect on mining speed whatsoever but may make it boot.

[flatronw]

Yes been there, but there is no option in the Bios on the Gigabyte 990XFA-UD5 (right up to the latest F8) to adjust PCIE Latency.