Editor's note: since publishing this article on 30/09/2005 the following addendum was added on 5/10/2005:
It has come to our attention from NVIDIA that Intel's future 975X platform may not be supporting both CrossFire and SLI afterall. More news as we get it.
It may have escaped some notice, but this month to a little fanfare ATI launched CrossFire. The low key unveiling didn’t actually come with any announcement, but we did receive the golden goods of a complete CrossFire setup in the mail, motherboard and all.
So why the low-key launch? This is ATI’s answer to SLI, surely it’s something to shout about? Unless, of course, there actually isn’t much to get excited about.
Getting a working system up and running proved quite a kerfuffle – we had to change RAM, lower memory timings and boost the cooling of our Athlon 4000+ test-bed processor just to get Windows installed stably. To be fair, this is reference hardware and we expect such problems to be ironed out by the time the product ships.
When we did get a system up and running it was clear that, at least at this initial stage, CrossFire is not going to be that attractive. We’ve been drowning in NVIDIA’s 7800GT and GTX cards for the past few months and have grown very used to the incredible quietness that these powerful beasts can muster. So to hear two X850 XT cards doing an impression of a hairdryer proved an instant turn off.
It wasn’t like we were looking forward to awe-inspiring performance, either. ATI states that CrossFire is to rival NVIDIA’s 6800 cards – an obsolete chipset -- underlining the lateness of ATI’s dual-card launch. Indeed, we couldn’t even make much of a comparison with the 7800 cards as the glorious HDR rendering that Far Cry offers isn’t supported. However, of note is that the driver supports anti-aiasing of up to 14x (NVIDIA cards are limited to 8x).
Testing
Our test bench used the reference ATI Xpress 200 CrossFire motherboard with two X850 XT graphics cards, an Athlon 64 4000+ processor, 1GB of PC3200 RAM and a 36GB WD Raptor – a speedy-enough system to rid us of any latency problems and bottlenecks.
We used three games: Far Cry, Doom 3 and Half Life 2. We ran each game test at the maximum 14x Anti Aliasing (AA) and 16x Anisotropic Filtering (AF) settings. We also ran each game test at 8x AA and 16x AF to compare to the top level performance of GeForce 7800 cards (note, though, that 7800 cards also had Transparency SuperSampling turned on and ran Far Cry with a maximum HDR setting of 11). Finally we ran all of our tests at a basic 4x AA and 8x AF to compare how much faster two cards in CrossFire ran compared to a single X850 XT card. All game tests were run both at 1280 x 1024 and 1600 x 1200 resolutions.
Our final test saw 3D Mark 05 run at 1280 x 1024 at default settings with CrossFire turned on and off.
Results
Test rig: AMD Athlon 64 4000+; 1GB PC3200 RAM; 36GB WD Raptor
With 14x AA and 16x AF all of our games proved playable at 1280 x 1024 with Half Life 2 scoring 35.2 fps and Far Cry 32.9 fps. Doom 3 teetered on the brink with 23.2 fps. At 1600 x 1200 Half Life 2 dropped to 27fps, Far Cry to 12.9fps and Doom 3 wouldn’t complete the test. The difference that 14x AA makes is debatable. We noticed a slightly smoother gun in Far Cry but nothing you wouldn’t notice without pausing the action and scrutinising every piece of the screen.
At 8x AA and 16x AF Half Life 2 ran at 38.3fps and 29.3 fps at 1280 x 1024 and 1600 x 1200 respectively. This compares with 46.6fps and 32.6fps scored by a 7800GT and 28.5fps and 14.9fps against a single 6800 Ultra. In Doom 3 31.3fps was scored at 1280 x 1024 -- again, it wouldn’t complete our 1600 x 1200. This compares with 36.6fps from a 7800GT and 23fps from a 6800 Ultra. In Far Cry it managed 39.2fps and 27.7fps compared with 51.9fps and 39.6fps from a 7800GT and 35.5fps and 24.9fps from a 6800 Ultra (remember though that the NVIDIA cards were performing a tougher test).
In our more-standard tests at 4x AA and 8x AF we saw impressive percentage differences. In Doom 3 the CrossFire set-up ran 49 percent faster at 1280 x 1024 and 63 percent faster at 1600 x 1200. In Half Life 2 the differences were 40 percent and 50 percent. In Far Cry the difference was constantly 22 percent. In 3D Mark 05 a single card scored 5954 3D Marks while CrossFire scored 8614 – a difference of 45 percent.
Enabling CrossFire is a simple proceedure
Conclusion
If you already own CrossFire-compatible card, there are obvious frame rate benefits to using a second one. But this is only on paper. In reality, you’ll need to spend an extra $700 or so on an X850 XT plus an extra couple of hundred dollars on a compatible motherboard. Quite simply you’d be mad not to plump for a cheaper, faster, feature-packed 7800 card.
CrossFire may become more tempting when Intel releases its 975X chipset which supports both it and SLI. Furthermore, if, in the next few months, the new Radeon X1800 (formerly R520) card turns out to wipe the floor with a 7800 GTX we might be saying that CrossFire is worth buying in to. However, for now certainly, CrossFire can be confidently described as Dead On Arrival. It’s a great technology when paired against the 6800 range, but it’s too little too late with NVIDIA’s new 7800 beast.
Can you spot the difference between 8x (left) and 14x (right) anti aliasing?