Pushing a Rig to its Limit: Quad SLI with 9800 GX2

Sometimes it’s the little quirks in life that sneak up on you and change the way you look at the world. The past couple weeks have done that in testing all this new high end gear. Sure, we’ve had our problems testing bleeding edge stuff before, but in putting all of this from CrossFireX through 9800 GX2 Quad SLI to the test, we’ve gotten ourselves lost in some other dimension of existence. It’s the only explanation really. Like Holmes would have said … whatever remains, however improbable … But I’m getting ahead of myself.

Skulltrail (the D5400XS Intel board we’re using that runs both CrossFire and SLI) rivals Frankenstein’s monster. From the 2x LGA775 sockets, FB-DIMMs, and NVIDIA nForce 100 PCIe chips, it’s not for the feint of heart. We’ve been determined to test on a single platform to compare CrossFire and SLI and trying to work out some kinks has given us a little trouble. AMD and NVIDIA and Intel have all worked with us to try and make things go more smoothly (thanks everyone), but there are still some things that we just can’t explain going on.

After loads of nearly useless testing and many conversations with different people, we set out on a trail of mystical discovery that has unlocked secrets of the universe here-to-fore untold. We’ll get to that in a bit, but first we’ve got to stop and take a look at what we are covering today.

Quad SLI. NVIDIA would like us to tell you it’s the new hotness. Certainly, without even opening a page of this review you should all know that this is the top of the top of the line and nothing is faster right now. But we do need to answer a few key questions about this $1200 setup: how does it scale from two GPUs to four, how does scaling compare to CrossFireX, and what kind of performance and value does this solution actually offer.

Honestly, we also have to acknowledge from our previous review of the 9800 GX2 that a single card is enough to run almost any game at maximum settings … that is, with the glaring exception of Crysis. Can Quad SLI change that? From what we saw in our CrossFireX testing from AMD, we would have thought not. However, NVIDIA has managed to get Crysis to scale across all four GPUs despite the interframe dependencies that make it so difficult. Is it enough to run Crysis at a decent resolution with all the eye candy turned on?

Let’s find out …

In almost every game other than Crysis, we don’t have a need to move beyond one 9800 GX2 (or 8800 GT/GTS/GTX/Ultra SLI). And in Crysis, we aren’t simply going to trust NVIDIA when they say we should see 60% scaling. We need to actually make it happen ourselves. The fact that we’ve run into some pretty strange problems doesn’t bode well for the solution in general, but we are willing to see what we can do to make it perform near to what we expect before we cast final judgment.

At the same time, that final judgment must include all the facts about what you gain from Quad SLI for the money. If it makes Crysis smooth as butter at Very High settings (it is actually playable even with the 40 average FPS system limitation), then that is something. But $1200 for a Crysis accelerator is a bit of overkill. NVIDIA has made the point to me that $1200 spent on graphics cards is better placed than $1200 spent on an Extreme Edition CPU. That isn’t a particularly compelling argument for us as I don’t believe we have ever recommended the purchase of an Extreme Edition processor (except for overclocking enthusiasts, perhaps). You certainly don’t get what you pay for unless you really need it for a specific CPU heavy workload. Content creation, engineering, math, and workstation applications might be a good fit, but certainly not gaming and especially not in a world where the more extreme you get the more cores you have.

Which brings me to a side rant. Parallelism is a good thing, but neither Intel nor AMD can ignore the single-threaded code path. Not everything can be split up easily, and every thread will always be limited in performance by the speed of the core it is running on. Of course, specialized cores on a heterogeneous processor would help, as would dedicated hardware. That just makes us lament the death of the PPU through the NVIDIA acquisition even more. But I digress.

On the topic of 9800 GX2 Quad SLI, there are benefits aside from the potential of Crysis that we haven’t covered here. NVIDIA has enabled AA on S.T.A.L.K.E.R., but it is very processing and memory heavy. Quad SLI could enable playable frame rates at higher resolutions with 2xAA enabled. With Clear Sky coming out soon, this could be a good thing for fans. You also get SLI AA modes. These do offer a benefit, but AA has diminishing returns at higher resolutions, and especially at higher AA levels. We will be testing SLI AA again at some point, but we want to look at both image quality and performance when we do so.

These cards also act as incredible space heaters. That may not be important right now with summer coming on, but any of our readers that live at the North Pole (Hi Santa! I've been good!) or in Antarctica (sentient penguins running Linux, for example) might appreciate the ability to turn down the thermostat while they sit next to their toasty Quad SLI system.

The bottom line right now is that this is not a solution for most people. Unless we see great scaling in Crysis, there are only a few other compelling features that can currently be enabled through the use of Quad SLI. Sure, it might handle future games with ease, but we always advise against trying to future proof when it comes to graphics. That’s always a path that leads to heartache and the hemorrhaging of money. Just ask previous 7950 GX2 Quad SLI owners about how happy they've been with support and performance over the past year. If you aren’t obsessed with Crysis, skip it. If you are obsessed with Crysis, we’ll get back to you with some numbers on what performance is like once we find a system we can get some headroom on: I’ll have 790i this week and I’ll be hard at work testing it out.