Strange Multi GPU issue

[mojo_jojo_mark]

Hi, Wonder if anyone has experienced this (currently using the latest demo release)

With Sli DISABLED and Octane setup for multi-gpu I am getting the exact performance figures on all scenes, e.g benchmark scene with one card has the same rate as when the multi gpu's are setup .....the strange thing is with 2 instances of GPU-Z enabled you can see each cards load is around the 90% mark and the memory load is identical on each thus are working side by side...

Using 2x GTX 280's, latest nvidia drivers on a fresh install of 7. Have tried everything from setting physx to one card then the other followed by off. With NVIDIA's latest control panel the Sli menu has been improved and you can see for sure the exact setup which is how I understand the issue must be somewere else.

Its as if I'm running 2 instances of the same scene but can only see the results and performance of 1........if that makes sense!?

[radiance]

with 2 identical cards you should have a 1.6 to 1.7x speedup, with fermi cards 1.9x
if this is not the case there's something wrong, like you say, play with your SLI config / disable it, and apparently one has to enable physx to get the 2nd card working, although on other systems it seems to be the inverse.

Radiance

[mojo_jojo_mark]

Thanks Radiance

But the bizzare thing is , the second card is working but the sample rate the speed etc, its exactly the same not even a slight improvement.

as you can see here everything's functioning, both cards being taxed...every combo has been used in the physx part.. Cuda has also been enabled for All in the other section....
http://img576.imageshack.us/img576/9132/capturehb.jpg

the 8.19 megasamples...I get 8.40 with one card...very strange

[radiance]

it's indeed very strange.
maybe try the latest drivers ?
do you have an sli bridge connector on your 2 cards ?

Radiance

[Amplitude]

you're using the very new 25x.xx driver generation right? this is interesting, maybe they introduce some kind of performance hit?
Have you tried with the 197.13 developer drivers or the 197.45 whql ?

[mojo_jojo_mark]

I was thinking the latest drivers but I have only updated today..Ive tried with the bridge off too that was my first thought as it may have been sync'ing the cards to do the exact same samples or something. :S

I will try rolling back the drivers later on tonight to see if its because of them but already have doubts. I also just noticed ever couple of seconds 100mb's builds up extra on each card then gets dumped

[radiance]

try with 197.45 whql

Radiance

[mojo_jojo_mark]

I just changed from the 197.45's ye to the 257 release, Looks like I need to double back Im sure the issue was present on both for me. If its a performance hit on the 256's then ouch....2 cards at 90% = 1 card at 99% for me

[mojo_jojo_mark]

Will try that now radiance and let you know

[Amplitude]

by the way it would be a good idea to put your configuration details in your signature, it can be handy for people trying to help you