ASUS Rampage IV Formula concern *SOLVED*

[KingDazza]

Hi,

Any ideas why the top PCIe lane would run my HD7970 DD Black Edition slowly - its rated at PCIe x16? If I put the card into the 2nd PCIe x8 or the third PCIe x16/x8, then full performance is delivered. I don't see it being driver related as I've tried this out on two separatete win 7 installs with same result. Also if card is in the problem lane closest to the CPU, then I sometimes get slow EFI screen navigation.

Does this lane need more power via the 4pin EZ mobo plug?

Is it normal for a mobo just to prefer certain lanes for single GPU set ups, when there is a choice of 4 PCIe lanes?

All is at stock and with a 3820. No stability issues whatsoever. Just hampered gpu performance in top lane closest CPU.

Any help appreciated, cheers!

 

[Pr3d4t0r]

the x4 even compared to x16 will not be more than a frame difference in games like bf3 maxed etc. as its still more than enough bandwidth to use, regarding the slots, the closest to the cpu would be a good choice if your a performance maniac that needs that single fps, but i like to slot it in a bit further down so it can get more cooling, the only thing i can think of is that the motherboard options somehow reduce the performance, try stock mobo settings and see if that helps

 

[KingDazza]

Yeah I'm running stock. GPU-z reports the lane fine as x16 and version 3.0. I agree, its just the mobo being a bit weird with that lane, when paired with the 7970. I've been running my xfi card in there and its fine. So no worries really, just a strange "glitch" if you like.

Maybe a future BIOS update will change things. Who knows, she'll probably stay as she is now anyway. No need to move the gpu back up there.

 

[KingDazza]

Interestingly, a new BIOS 1202 update has just been released. And it makes special mention of PCIe lanes and the HD7970. Don't you just love latest tech

 

[KingDazza]

Right, fully solved this now and thought I'd post incase any body comes reading with similar issue. This is a compatibility conflict issue with x79 and PCIe 3.0. Running the lanes in PCIe Gen 2 mode (sets them to behave as 2.0 and not 3.0)not only resolves the issue I had but has given me an extra 4% performance boost.

So there we go - always consider setting PCIe lanes to GEN2 mode and away from the default GEN3 mode. Alls well that ends well

 

[Pr3d4t0r]

Glad to hear ;D

 

[tharionos]

should i do this to ? or is this a issue that only happens to sum people ? or is it a recommended fix for evryone

 

[KingDazza]

Only if you have issues. You can always try both modes and see... I'm going to be trying out a GTX680 tomorrow and will be interesting to see if it behaves the same as the HD7970 does in GEN3 mode.

 

[Larriy]

[font=Verdana, sans-serif, FreeSans]or is this a issue that only happens to sum people ?[/font]

 

[KingDazza]

Sorry for late reply - but I've since found out that my motherboard was definitely faulty. I've since moved over to z77. So difficult to now say what issues I had were due to the motherboard faults, chipset, ASUS board specific etc etc.

I have none of these issues on the z77 board I'm using.