Why can't I get my fifth PCIe slot to work (on two boards)?

[DogeNukem]

So I thought I was being clever by finding a couple of good deals on Gigabyte boards with five slots total, as they were half the price of the BTC specific boards (I wasn't going to install more than 5 cards anyways).

The model numbers are http://www.gigabyte.com/products/product-page.aspx?pid=3483#ov and GA-Z68AP-D3 http://www.gigabyte.com/products/product-page.aspx?pid=3483#ov

On both boards I tried all combination of cards, and risers (all powered USB risers).

On both boards one card would always not install.  This would randomly seem to vary by slot and by card, almost with each reboot.  Strange thing is this happened on both machines.

I used neosmart's tool to disable driver signature verification, but that didn't help.  This seemed to be a different issue as on both boards, four cards were no issue (all slots work, just not all five) but the fifth one always faltered.  I thought since I was using powered risers this would not be an issue.

Perhaps there was an IRQ issue or something similar, so I disabled every extra peripheral in BIOS (audio, extra SATA ports, USB, etc).

I am using a 1200W PSU in one rig (powering a 7970 and three 7850s) and a 1600W PSU powering the other (4 7950s).

Any ideas?  Thanks in advance!

[Masejoer]

I used neosmart's tool to disable driver signature verification, but that didn't help.

So you're running Windows. Unless using older drivers or modified newer ones, Windows 7 is limited to 4 7900-series video cards and Windows 8 is limited to 5. I assume since you're disabling driver signature verification that you're already using modified drivers?

https://bitcointalk.org/index.php?topic=193695.0

[Masejoer]

Not true.

I'm running 6 7950's on Win 7 64 Pro on a AS Rock H81 BTC Pro Motherboard and I have 5 7950's on an MSI 990FXAGD65 agai with Win 7 64.


It's the limitations of that particular old board he using.


~BCX~

Driver version?

Straight from AMD's release, driver versions after ~13.xx (it's a toss up for 12.8 and 13.1) will just throw a yellow exclamation mark in the device manager on videocards 5+ in Windows 7. Modified drivers take care of this issue. One of mine with that issue is running the same Asrock BTC mATX board using powered risers. 13.12 modified works fine though.

Not saying you're wrong, but I can't find enough details for that specific motherboard. It does share bandwidth between two of the x1 slots and the x4 slot (lower "x16" slot). When all three are populated, the "x16"/x4 slot runs at x1. So we have one x16 slot direct to the CPU, second x16 slot is running at x1, and two x1 slots are running at x1. Since PCIEX1_1 isn't mentioned in sharing bandwidth, it likely has its own lane. I think the Z68 motherboard should handle 5 videocards fine. I haven't looked into the other one. Therefore, I'd look at driver version.

[broken_pixel]

I ran 5 7950s on a GA990-FXA-UD5, you need to use 12.6 driver as any driver after that only supports 4 GPUs. They will show in device manager but will not be able to utilize them.

Some boards need the pcie slot shorted to get more working and it always depends on the order also.

[Masejoer]

My response was to you saying that Win 7 was limited, it's a driver issue.

12.8 and win 7 64 will run 6 cards in 7800/7900 series without an issue.

Then you didn't read the post. "Unless using older drivers or modified newer ones, ..." . Those limitations are based on the driver and Windows versions. Everything I can see points to the OP's issue as being driver related, not motherboard as you had initially mentioned. This may not be true if he is disabling driver signing verification so that modified drivers may be installed. He did not provide enough information.

[Masejoer]

It doesn't matter what driver you are using, Win 7 is not the limiting factor, it's the driver.

Probably just a language barrier thing.

Perhaps it is. Newer drivers are limited to 4 cards in Win7 and 5 cards in Win8. I don't care where the limitation currently resides - the driver has those limits on those environments. I have dedicated mining systems running each OS and have seen the issues firsthand. I'd use Linux if I didn't already have a custom setup for Windows that allows me to instantaneously update all my miners from my phone (send three characters and they respond to my new settings/new mining app files/etc). 

I'm sure you will agree with the information available online for the OP's motherboards, the limitation does not appear to be motherboard. He needs to use a different version. If he wants five cards working, he would need Windows 8 if he wants to run the latest stock drivers.

[DogeNukem]

Thank you everyone for the extremely detailed responses.

My apologies for not providing sufficient information earlier.

I am using the newest 13.xx drivers, and will try an older version once I'm home later today.  Seems like the z68 chipset should be fine for five cards but a bit uncertain if the s775 shares the same fate.

Will let you know.

Cheers and thanks again!

[DogeNukem]

Update: Worked on the S775 board!  Now just need a 16x riser to try the other one (not taking any chances w/ the shorting route  )

Now if only there was an easy fix for these temps in the coming summer heat lol