GeForce 9800 GTX and 3-way SLI: May the nForce Be With You
by Derek Wilson on April 1, 2008 9:00 AM EST- Posted in
- GPUs
The Test
Once again we used the Skulltrail system for most of our comparisons. We’ve added on the 790i board for 3-way SLI performance scaling tests.
I didn’t believe I would be saying this so soon, but our experience with 790i and SLI has been much much worse than on Skulltrail. We were plagued by power failure after power failure. With three 9800 GTX cards plugged in, the system never got up over 400 W when booting into windows, but after a few minutes the power would just flicker and cut out.
It didn’t make sense that it was the PSU size, because it wasn’t even being loaded. We did try augmenting the PSU with a second one to run one of the cards, but that didn’t work out either. The story is really long and arduous and for some reason involved the Power of the Dark Side, but our solution (after much effort) was to use one power supply for the system and graphics cards and one power supply for the drives and fans. Each PSU needed to be plugged into its own surge protector and needed to be on different breakers.
The working theory is that power here isn’t very clean, and the 790i board is more sensitive to fluctuations in the quality of the power supplied (which is certainly affected by the AC source). Isolating breakers and using surge protectors was the best we could do, and we are very thankful it worked out. It seems likely that a good quality 1000-1500 VA UPS would have been enough to provide cleaner power and solve the issue, but we didn’t have one to test with.
Once we handled this we were mostly able to benchmark. We could get a good 15 minutes of up time out of the system, but after repeated benchmarking instability crept back in and we’d need to wait a while before we tried again. The majority of these problems were on 3-way and Quad SLI, but we did have a hiccup with a two card SLI configuration as well. We didn’t have any trouble at all with single card solutions (even single 9800 GX2 solutions).
Before anyone says heat, we were testing in an open air environment in a room with an ambient temp of about 15 degrees C, with one 120mm fan blowing straight into the back of the GPUs and another blowing through the memory (we did take care not to interfere with the CPU HSF airflow as well). The graphics cards did get warm, but if heat was the issue here, I’d better get a bath of LN2 to run this thing submerged in ready.
It is very important that we note one more time that this is the C0 engineering sample stepping and that NVIDIA explicitly told us that stability might be an issue in some situations. The retail C1 stepping should not have these issues.
Here’s our test setup:
| Test Setup | |
| CPU | 2x Intel Core 2 Extreme
QX9775 @ 3.20GHz |
| Motherboard | Intel D5400XS (Skulltrail) |
| Video Cards | ATI Radeon HD 3870
x2 NVIDIA GeForce 8800 Ultra NVIDIA GeForce 9800 GTX NVIDIA GeForce 9800 GX2 |
| Video Drivers | Catalyst 8.3 ForceWare 174.74 |
| Hard Drive | Seagate 7200.9 120GB 8MB 7200RPM |
| RAM | 2xMicron 2GB FB-DIMM DDR2-8800 |
| Operating System | Windows Vista Ultimate
64-bit SP1 |
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Jangotat - Friday, April 18, 2008 - link
The way they're setting this up is great but they need to fix a few things 1 use a 790i Asus motherboard 2 use OCZ 1600 platinum memory 3 let us see some benchmarks with 3-way 8800 ultra cards that would be sweetPlatinum memory has custom timings for asus, and asus doesn't have issues like EVGA and XFX do. And we really need to see the 3-way ultra setup to see what's really the best for crysis and everything else
You guys could do this right?
LSnK - Wednesday, April 2, 2008 - link
What, are you guys running out of zeros or using some ancient text mode resolution?Mr Roboto - Thursday, April 3, 2008 - link
Derek, you say that a 25% decrease in performance resulted from disabling VSYNC in Crysis and WIC. However you then say in the next sentence that performance gains can be had by disabling VSYNC? Maybe I'm misunderstanding?"Forcing VSYNC off in the driver can decrease performance by 25% under the DX10 applications we tested. We see a heavier impact in CPU limited situations. Interestingly enough, as we discussed last week, with our high end hardware, Crysis and World in Conflict were heavily CPU and system limited. Take a look for yourself at the type of performance gains we saw from disabling VSYNC".
Evilllchipmunk89 - Wednesday, April 2, 2008 - link
Seriously what about the AMD 790FX board? you will test the Nvidea cards on thier "home platform/790I" platform, But what not the ATI cards home platform. Obviously you can get more performance if you had the 790FX board that was made more specificly for the Radeon3870swhere you can tweek more aspects of the card. In an earlyer review you showed us that with nothing changed but the board the 780I outperformed the skulltrail on the Nvidia cards but you wint even mess with the ATI boards
just4U - Tuesday, April 1, 2008 - link
I dont quite understand why they just didnt go with a 512bit interface like on the X2's. That's what I was expecting anyway.One thing that has me surprised. I was checking my local store on the web for "new arrivals" (a feature where new listings appear daily) and saw the GTX and was thinking hey wait .. Annand hasn't even reviewed this yet and it's in stock???! wow. I imediately came here and there the review was :D So nvidia is trying to stay on top of the hard launch which is nice to see but mmmm.. still troubled by that no 512bit interface. To me it still seems like a GTS/512.
7Enigma - Wednesday, April 2, 2008 - link
And yet the GTS wasn't included in the review...deeznuts - Tuesday, April 1, 2008 - link
It's actually "lo and behold" and I'm not even sure it's being used right. You propably are, but essentially you're saying, "look, see, I looked, and saw ..."Olaf van der Spek - Tuesday, April 1, 2008 - link
So what is the cause of the vsync issue? I don't see an explanation of that.It'd be interesting to know why performance drops with vsync off.
finbarqs - Tuesday, April 1, 2008 - link
Haha Happy April Fools day!prophet001 - Tuesday, April 1, 2008 - link
you guys write some nice reviews on this website but the visuals are a little lacking. i guess when i read an RSS feed that talks about 9800 gtx triple SLI then i kinda expect to see at least a picture of a mobo with 3 cards on it and a uranium iv. i know, it's about the results, but more neat pictures would be nice :)