Quad SLI with 9800 GX2: Pushing a System to its Limit
by Derek Wilson on March 25, 2008 9:00 AM EST- Posted in
- GPUs
Overall Performance Scaling With 4 GPUs
Before we present the percent scaling when moving from SLI / CrossFire to Quad-SLI / CrossFireX, we need to make note of a few things.
First, the 9800 GX2 is a higher performance part and is going to run into CPU limitations more readily than the 3870 X2. This means that sometimes scaling won’t reflect the true potential of the NVIDIA solution.
Second, anything over 50% scaling shows that the game is running on all four GPUs. However, less than 50% scaling doesn’t mean that all four GPUs are not doing work. On the contrary, if two GPUs don’t scale near linearly, moving from two to three will likely not scale linearly as well, meaning you could be seeing work done on 3 GPUs at less than 50% scaling up from the single-card dual-GPU solutions we have here. Then adding a fourth GPU might not even bring the percent high enough to make it clear that four GPUs matter.
What more than 50% scaling means is that all four GPUs absolutely matter and the game scales well with a Quad solution. With that in mind, lets take a look at the numbers.
So this becomes very interesting when you hear that NVIDIA claims 60% scaling with Quad-SLI in Crysis when running at Very High settings. We ran these numbers at High + Very High shaders, as we really didn’t expect that Very High would be any more than a slide show. We’ll take a look at this later. For now, suffice it to say that High settings plus Very High Shaders is CPU bound even at 1920x1200 under Crysis. Very High settings are also playable with Quad-SLI, but more on that later.
The Oblivion without AA numbers on NVIDIA are low because a single 9800 GX2 actually outperforms the Quad-SLI until you hit 2560x1600. This beast is made for high res gaming as long as bandwidth doesn’t kill it. 2560x1600 with Crysis isn’t here yet (unless you want to turn the quality way down), but this is only for people with 30” panels. If the only thing you want to buy 9800 GX2 Quad-SLI for is Crysis then by all means save the cash and get a 1920x1200 panel. We certainly don’t recommend such flagrant spending for one title though, and if you want your money’s worth, you’ll want the biggest display possible.
So, CrossFireX doesn’t scale at all in Crysis, all of our AMD cards started crashing out of the World in Conflict benchmark, and CrossFireX won’t run with OpenGL games yet. (AMD will release a driver supporting this at a later time.)
Neither quad solution hits every mark perfectly. We’ll take a look in a minute to see what happens with Crysis at higher settings, but in Oblivion - since performance is actually lower than AMD hardware - we wouldn’t expect to see any sort of system limitation here.
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iceveiled - Tuesday, March 25, 2008 - link
I understand crysis is a good game to test the muscle power of video cards, but if anybody out there hasn't played the game yet and wants the best setup for it, please don't spend $1200 in video cards. I've played through half life 2 numerous times, call of duty 4 numerous times, and crysis only once. Once you get over the wow factor of the graphics, it's not that amazing of an experience....mark3450 - Tuesday, March 25, 2008 - link
In this and the last article on the 9800GX2 the following benchmarking data on Crysis @2560x1600 has shown up in a chart.9800GX2 - 8.9FPS
8800Ultra - 16.3FPS
8800GT - 12.3FPS
Now I look at this and I say the FPS scaling you get by adding a second card is generally around 50% to 60% in the best case scenario. If we assume that, then 2x 8800Ultra would be getting around 25FPS, which is getting into playable range especially with the motion blur that Crysis uses. Obviously this is assuming decent scaling, but this data just screams give it a try.
On a slightly realated note, I also see that the same Crysis chart shows that two cards scale roughly linearly with resolution up to to 2560x1600 (8800GT and 8800Ultra) while the others show a sharp drop at 2560x1600 (9800GX2, all AMD cards). This makes me ask the question what's different about these two groups of cards. One common feature I note is that the cards that scale linearly are all using PCIe 2.0, while the ones that have a sharp drop off @2560x1600 are using PCIe 1.x (the 9800GX2 is externally PCIe 2.0, but internally the two cards are connected via PCIe 1.x). Mabey it has nothing to do with the type of PCIe connection, but it certainly correlates.
Basically all this makes me think that for gaming at 2560x1600 I'm likely to be better off with two 8800Ultra's (or even 8800 GTX's) than I am with one or even two 9800GX2's (and since I and a lot of people interested gaming on high end rigs at 2560x1600 likely have a 8800GTX/Ultra already it would be far cheaper as well). This is of course all speculation since there are no reported benchmarks for 8800GTX/Ultra in SLI mode in these comparisons, which is why I like to request them. :)
-Mark
mark3450 - Tuesday, March 25, 2008 - link
Turns out hardocp has a review up athttp://enthusiast.hardocp.com/article.html?art=MTQ...">http://enthusiast.hardocp.com/article.html?art=MTQ...
(can't insert a proper link for some reason)
that compares 2x 9800GX2 with 2x 8800GTX's. The short summary is 2x 8800GTX's are better than 2x 9800GX2 at hi-res gaming. The 9800GX2's often have higher average frame rates than the 8800GTX's, but the 8800GTX's have much more consistent frame rates (the 9800GX2's often had there frame rates crash to unacceptable levels for short periods of time, whereas the 8800GTX were playable throughout).
Essentially it looks like I am better off getting a second 8800GTX rather than 1 or 2 9800GX2's for gaming at 2560x1600, and it's way cheaper to boot.
I will still wait till next week to see how the 9800GTX performs, but given the leaked info on it and recent history of anemic releases by NVIDIA I'm not holding out much hope for the 9800GTX.
-Mrk
zshift - Tuesday, March 25, 2008 - link
in the second paragraph you noted the skulltrail as having 2x lga775 sockets, but i'm pretty sure it has lga771 sockets only. if i'm mistaken, i apologize, if i'm right, please correct the error so other less knowledgeable readers don't receive false information.Tilmitt - Tuesday, March 25, 2008 - link
You guys shouldn't be using Skulltrail to benchmark games. It's not a gaming platform. Most games run slower on it than a single socket quad core systems due to the FB DIMMs. It provides a sub-optimal environment for both SLI and crossfire which negates any value that it might have for levelling the playing field there. I think the author is letting his personal desire to use the Skulltrail system get in the way of doing a proper review. The fact of the matter is that Skulltrail is slow for games and doesn't reflect how the vast majority of people would run their SLI and crossfire setups.As to the multi-GPUness, I think you'd have to be mad to buy them given the price and horrendous scaling. As always, the generation cards will mostly outperform a multi-GPU systems at less cost, less power consumption and more consistent performance across all games.
tynopik - Tuesday, March 25, 2008 - link
faint of heart, not feint ;)cactusjack - Tuesday, March 25, 2008 - link
This is my point. The testers here had "some problems" and these guys are very experienced and tecnically savy. They also have access to alot of PSU's ram etc etc to try if things dont work right. If it were a car or a television it would be sent back as what it is, a failure, and a lemon. Why do we accept it with PC parts.?Inkjammer - Tuesday, March 25, 2008 - link
Case in point, I have the 9800 GX2:* I can not run multiple monitors with SLI enabled. So I have to swap between my 24" monitor and my Wacom Cintiq 21". When I change over, the drivers won't auto-detect the resolution, and uses resolutions and hertz the Wacom doesn't support, and I get an "out of signal" error. I have to disable SLI to use my $2,500 art tablet as a secondary monitor.
* I'm a graphic designer, and I can't take screenshots anymore without them coming out garbled like this:
http://www.inkjammer.com/broken_screencaps.jpg">http://www.inkjammer.com/broken_screencaps.jpg
I could find workarounds, get a screen cap program or just disable SLI, but this is all basic functionality gone bad.
There are a LOT of little problems that could impede testing without being visible. The fact that SLI breaks basic functions like multi-monitor setups and screen capture in Vista is puzzling. These drivers feel like betas lacking basic functionality. If I even try Crysis with 8X FSAA my entire system crashes.
dare2savefreedom - Tuesday, March 25, 2008 - link
Did you report this to nvidia:http://www.nvidia.com/object/vistaqualityassurance...">http://www.nvidia.com/object/vistaqualityassurance...
Inkjammer - Tuesday, March 25, 2008 - link
I adopted from an 8800 GTX to a 9800 GX2, and I'm really frustrated with the drivers - there are a lot of issues with them running it in "SLI". There card has a lot of raw performance, but seeing it doubled up with two cards...Costs aside, it really seems like anything beyond 2 GPUs at this point and time is rather useless. The technology is there, but the drivers are still too immature and the rest of the tech it requires to be useful hasn't caught up to speed.