Widescreen Gaming Forum

I see there's been alot of threads basically saying it doesn''t work. I did some testing for myself, it does work however the fps are alot worse than when a single core is doing the rendering.

I think i read somewhere that kegetys said that sli should work in theory, there's nothing in the programming that should prevent it from doing so.

The setup i was testing :

vista x64
xfx 780i
2 x 8800gt 512mb
1x 8800gts 640mb
4x2gb ddr2-800 and 2x1gb ddr2-1200 (to compare the effect of mem bandwidth)
q6600@3600(400x9)


I just used unreal tournament 3 as a comparison, couldn't be bothered trying to get a benchmark that would work. Thought you guys might be interested in this rough comparison:

single 8800gt with th2go = ~40fps moving, 60fps stationary in a certain spot
single 8800gt, softth, ddr2-800 = ~20fps moving, 30 stationary
single 8800gt, softth, ddr2-950 = ~25fps moving, 35 stationary
single 8800gt, softth, ddr2-1200 = ~32fps moving, 42 stationary
sli 8800gt, th2go = ~80fps moving
sli 8800gt, softth = 5fps moving
sli 8800gt, softth, hypertransport link oc'd from 200 to 300mhz = 8-10fps moving


Seems memory bandwidth is quite beneficial. I believe 1200mhz ddr2 is the limit of the bottleneck for a single 8800gt, any higher won't really be utilized. A faster graphics card may see extra benefit from ddr3.

Also, FSB speeds made no difference to fps. Neither did dropping the cpu speed, so they musn't be fully utilized with softth.



Now to the point of my post, does anyone have any theories as to why sli is not performing? I thought it may be due to the 3rd pci-e slot running off the southbridge. However with a single 8800gt rendering and the side displays running through the 3rd pci-e, i got the same results as having the displays running off the second pci-e slot on the northbridge.

This would rule out that theory, however overclocking the hypertransport link (southbridge - northbridge link) saw an fps increase in sli. Though i spose something else could be happening which causes the increase.

Does anyone here own a 9800gx2 that could do a test? My theory was that fps may be alot faster if all the pci-e slots are on the northbridge. Therefore a 9800gx2 running in sli mode, aswell as a second display card in the 2nd slot, may work 'properly'.

My gts died so i'm waiting for a couple of passive 8600gt's to arrive before i can do further testing. I don't really want to pay for a 9800gx2 to test, if it may not work.

Also, crossfire results would be equally interesting.

Cheers

Theory: SLI is not designed to have a third video card, users have figured out a way around this, but I suspect that the memory bandwidth is not optimized in a SLI + 3rd video card situation, and instead of the image being moved across the PCIe x16 bus, it is moved thru slower system ram. Also the third video card is drawing both the left and right monitors (instead of just the right side) and has to pass thru the system ram doubling the work even more.

I got SLI + SoftTH working in Vista x64, but it did not perform as well as non-SLI in XP, probably because my third video card was a 8600GT and my two other cards are 8800GT's.

I did not get such poor results as illdrift did, the performance of SLI+SoftTH in Vista x64 was about 80% the rate of non-SLI SoftTH in XP. I did just update to the 174.74 drivers and those seemed to help.

I don't have a fast ATI card to try SLI + SoftTH in XP (yet).

So for now running XP + SoftTH + non-SLI 2 x 8800GT's. Runs Assassin's Creed at 3840x1024 smootly, so no complaints!

Conclusion: Triplewide + SLI is best on TripleHead2Go, let's hope they come out with a higher resolution model soon. Until they do, I will probably keep using SoftTH.

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Core i7-8086K @ 5.0 Ghz | H60 | Nvidia GTX 980 Ti 6GB | Soundblaster Z | Asus Z370-A

16GB DDR4 | Win10 x64 | 3x27" Asus IPS @ 5760x1080 | Samsung 970 1TB NVMe

Good theory, it would be interesting to see how ddr3 would compare in this situation.

I saw slightly better results having both side displays on the seperate 'display' graphics card. I got a 2-3fps increase, compared to having one of the side outputs on the rendering card. This was at ddr2-1200, at lower ram speeds the opposite occured where the fps dropped by having both side displays on the 'display' card. This leads me to believe that there is just enough memory bandwidth at ddr2-1200, and that the slightly better fps is achieved because the 'rendering' card does not have to output an additional display, such as happens with single screen gaming.

Still, would be interesting to see whether the ddr3 bandwidth is beneficial in sli.


I'll give the different drivers a go as you mentioned tricky.


Personally i'm kinda over the triplehead2go. I still prefer surround gaming, it's just the low pixel limitation and low hz. Except for new games, a single graphics card is usually adequite to surpass 3840x1024x60 with no aa. For newer games like crysis, for whatever reason multiple gpu's don't scale nearly as well, so i can't really justify paying for multiple gpu's for single screen gaming.

Also, considering 1680x1050 is now the new size for the best value lcd's, makes the th2go seem outdated. I'm not sure about everyone else, but i don't see matrox delivering a new product anytime soon. Since the th2go has maxed the bandwidth of a dual dvi link, they'll either need a new connection type for monitors, or somehow link multiple outputs.