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Old 08-01-05, 02:49 PM   #47
zakelwe
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Join Date: Dec 2002
Posts: 768
Default Re: Nvidia 6800GT SLI investigation

Hi Chris,

Here's the compares . Firstly, I am running 2 MSi 6600 Diamond cards which have the 1Ghz 2ns GDDR3 memory on them rather than the standard 3.6ns DDR memory, so when running at 500/1000 they represent in effect a bridgeless version of the GT's for a nice compare.

Here's Lost circuits 6600GT's in 2001

http://www.lostcircuits.com/video/6600gt_sli/5.shtml

Nature none Sli = 95fps v 177fps SLI ( 87% gain )

Single fill rate none Sli = 1774 v 3483 Sli ( 96% gain )
Multi fill rate none Sli = 3931 v 7670 Sli ( 95% gain )

I tried to replicate his software so although my drivers are 77.72 for bridgeless Sli use I had Sp1 A and Windows XP Pro etc. I used an Fx 55 rather than his San diego 4000. I used memory at 200x12 2-5-2-2.

Here's my Sli setup set to single GPU

http://service.futuremark.com/compare?2k1=8669422

and here my Sli set to multi GPU

http://service.futuremark.com/compare?2k1=8669428

to summarise

Nature none Sli = 96fps v 98fps SLI ( 2% gain )

Single fill rate none Sli = 1799 v 3316 Sli ( 84% gain )
Multi fill rate none Sli = 3930 v 6732 Sli ( 71% gain )

Compared to his none SLi scores for nature and framerate I match really well as expected . For Sli in fill rates I also think those compare well as of course I will not gain as much due to being bridgeless and not as efficient ( though it is interesting to note multi texture fill rate gets a bigger hit .. why is this ? )

However what goes to explain nature ? It seems either it is not working or there is some bottleneck he does not have on his system. When I use Split Frame with the on screen green line it does go up and down indicating something is happening, but with the AFR as standard I do not know how you tell it is working, I have to assume it is.

Because I cannot explain this it is really bugging me, by all evidence it should be gaining as fill rates are up as expected. Dragothic Dx7 test also shows no improvement and that should also show a noticable gain in draothic low.

Both 03 and 05 work fine with Sli massively pushing up performance.

I'm totally puzzled.

Any thoughts ?

Regards
Andy
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