HD 4850 + P6T Deluxe v2 Crossfire Problem

[Red Irish]

Hi folks,

Motherboard: Asus P6T Deluxe v2 with latest bios.

Crossfired HD4850's with latest drivers:

http://www.club3d.nl/products/...h_id.cfm?product_id=49

OS: Vista 64

I am experiencing a problem with my Crossfired HD 4850's. In Catalyst, the max bus setting for the primary adapter appears as x8. On this board, the max. bus for the primary adapter should be x16. The bios only allows me to alter the bus settings for cards on the 2nd and 3rd slots (x8/x8 or x16/x1). The 2nd card is set to run at x16 in the bios and appears as such in CCC. Ati's 9.8 drivers have failed to resolve the issue.

Later on, I will experiment with taking out both cards and trying each separately, but before that, I wanted to know if anyone else has experienced a similar problem with their primary adapter in CCC. I'll also use CPU-Z when I get back home to see whether or not it corroborates the x8 max. bus setting for the primary adapter. My only hope is that the problem does not reside with the motherboard.

Any input would be much appreciated.

 

[Red Irish]

Update: I removed both cards and tested them in the first slot - both ran at x16, so it would seem to be a Crossfire issue rather than a problem with the board. I think I'll stick to one card, sell the other and steer clear of Crossfire in the future.

 

[Modular]

There are many motherboards that reduce the bus speed (for Crossfire and SLI) to 8X when in those respective modes. Looking up the specs on your motherboard (on Newegg, ASUS website is sloooooow) isn't giving me much info. They note the specs for 3x usage of the PCI-e slots, but not 2x. Have you tried contacting ASUS?

Also, from what I've read on these boards, cards like the 4850 don't really benefit from the x16 lanes over x8. The performance benefits of using Crossfire with those particular cards will far outweigh the frustration of them not working in x16 modes.

 

[thilanliyan]

It's odd that it would do that but as Modular said, a 4850 isn't really going to saturate that PCI-e bus so XFire would still be beneficial. Have you updated the motherboard BIOS as well?

 

[Red Irish]

Originally posted by: Modular
There are many motherboards that reduce the bus speed (for Crossfire and SLI) to 8X when in those respective modes. Looking up the specs on your motherboard (on Newegg, ASUS website is sloooooow) isn't giving me much info. They note the specs for 3x usage of the PCI-e slots, but not 2x. Have you tried contacting ASUS?

Also, from what I've read on these boards, cards like the 4850 don't really benefit from the x16 lanes over x8. The performance benefits of using Crossfire with those particular cards will far outweigh the frustration of them not working in x16 modes.

I didn't contact Asus. I was under the impression that x58 boards were defined by the fact that both graphics are given a x16 bandwidth when operating in Sli or Crossfire (hence "x" rather than "p"). In any event, I've decided that I would be better off with a single fast card. As you say, it has been a frustrating experience.

 

[Red Irish]

Originally posted by: thilan29
It's odd that it would do that but as Modular said, a 4850 isn't really going to saturate that PCI-e bus so XFire would still be beneficial. Have you updated the motherboard BIOS as well?

Yes, I am running the latest version and used the 9.8 drivers in my last attempt.

 

[Golgatha]

Install both cards, uncheck crossfire X in the CCC and see what speed CPU-Z and CCC are reporting for the primary graphics card.

X58 motherboards all run dual graphics solutions in 16x/16x mode AFAIK. FWIW my X58 vanilla ASUS P6T runs 16x/16x/1x for the three graphics slots just fine. I have 2x 4870 1GB and a PCIe 1x Intel NIC installed in the three physical 16x slots.

Sounds like a bug in the BIOS to me.

 

[Red Irish]

Originally posted by: Golgatha
Install both cards, uncheck crossfire X in the CCC and see what speed CPU-Z and CCC are reporting for the primary graphics card.

X58 motherboards all run dual graphics solutions in 16x/16x mode AFAIK. FWIW my X58 vanilla ASUS P6T runs 16x/16x/1x for the three graphics slots just fine. I have 2x 4870 1GB and a PCIe 1x Intel NIC installed in the three physical 16x slots.

I did that. I unchecked Crossfire and installed a single card on the primary slot: each single card was receiving x16. When I unchecked Crossfire with both cards installed, the primary slot remained at x8.

I'll see what Asus have to say about this issue.

Should I RMA the board?

Thanks for the input.