AMD's CrossFireX: Tri & Quad GPU Preview
by Anand Lal Shimpi on February 21, 2008 3:00 AM EST- Posted in
- GPUs
The Test
| Test Setup | |
| CPU | AMD Phenom @ 2.6GHz |
| Motherboard | MSI K9A2 Platinum |
| Video Cards | ATI Radeon HD 3870 X2 ATI Radeon HD 3870 |
| Video Drivers | Catalyst 8.1 (Modified for CrossFireX Support) |
| Hard Drive | Seagate 7200.9 300GB 8MB 7200RPM |
| RAM | 2x1GB Corsair XMS2 DDR2-800 4-4-4-12 |
| Operating System | Windows Vista Ultimate 64-bit |
We ran the following games in their corresponding quality settings:
| Game | Resolution | AA | AF | Detail Settings |
| Half Life 2: Episode Two | 2560 x 1600 | 8X | 16X | Highest in-game |
| Unreal Tournament 3 | 2560 x 1600 | 0X | 16X | Highest in-game |
| Bioshock | 2560 x 1600 | 0X | 1X | Highest in-game |
| Call of Duty 4 | 2560 x 1600 | 4X | 16X | Highest in-game |
| Crysis | 1920 x 1200 | 0X | 1X |
High Quality defaults |
The graph below shows the performance levels you can get from a single GPU all the way up to four:
Obviously the biggest jump comes from one to two GPUs, but we still see some reasonable gains going from two to three. The value of a fourth GPU is simply nonexistent in most of the cases.
| Number of GPUs | HL2 | UT3 | Bioshock | CoD4 | Crysis |
| 1 x Radeon HD 3870 | 39.3 | 46.7 | 36.9 | 25.3 | 14.0 |
| 2 x Radeon HD 3870 (1 X2) | 71.9 | 84.1 | 63.2 | 50.0 | 26.2 |
| 3 x Radeon HD 3870 (2 X2 + 1) | 93.3 | 112.7 | 86.7 | 72.2 | 26.4 |
| 4 x Radeon HD 3870 (2 X2) | 102.2 | 114.6 | 92.5 | 93.2 | 27.7 |
Let's put some percentages with the graph above to put things into perspective:
| Configuration | HL2 | UT3 | Bioshock | CoD4 | Crysis |
| 2-way CF Improvement over 1 card | 83% | 80% | 71% | 98% | 87% |
| 3-way CF improvement over 2 cards | 30% | 34% | 37% | 44% | 0% |
| 4-way CF improvement over 3 cards | 10% | 3% | 7% | 29% | 4% |
| 4-way CF improvement over 1 card | 160% | 150% | 151% | 268% | 98% |
The move from one to two cards generally yields a healthy performance improvement, but the gains taper off as we look at the performance added by a third GPU. Call of Duty 4 is the only game that shows solid gains with 4 GPUs (29% over a 3-GPU configuration), the rest of the titles show mostly single-digit percentage improvements. Once again we see that Crysis simply needs new, faster GPU architectures - four GPUs does absolutely nothing for this game.
Remember our 3-way SLI review from earlier in the year? Although the test systems were very different, the GPU-bound scaling should be comparable (if anything, NVIDIA should have the advantage of being run on an Intel system). Here's a quick look back at some of the comparable benchmarks:
| Configuration | UT3 | CoD4 |
| 2-way SLI Improvement over 1 card | 84% | 90% |
| 3-way SLI improvement over 2 cards | 20% | 28% |
| 3-way SLI improvement over 1 card | 121% | 143% |
Single to dual GPU scaling is similar with SLI as CrossFire, but the 2-way to 3-way gain is better on CrossFireX. NVIDIA's quad-SLI is not yet available so we're not sure how the 4-way scaling will compare, but so far it seems like CrossFireX is doing quite well in the pure numbers game.
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Pirks - Thursday, February 21, 2008 - link
Do they speak English in "what"? (C) Pulp FictionNever mind, just kidding :)
Griswold - Thursday, February 21, 2008 - link
What!?skiboysteve - Thursday, February 21, 2008 - link
"What were 70 - 100% gains from 1-to-2 GPUs are more than cut in half, becoming 30 - 45% gains when you add a third GPU"this should be expected...
If each card provides 50fps in an ideal case...
1card at 50 fps
2card at 100fps = 100% improvement over 1 card
3card at 150fps = 50% improvement over 2 cards
4card at 200fps = 33% improvement over 3 cards
The most it can possibly provide is 100%, 50%, 33% improvements at 2,3,4 cards.
Noting that, COD4 scales incredibly well.
dustwalker13 - Thursday, February 21, 2008 - link
exactly what i was thinking ... cod almost scales ideally right up to 4 gpu's ... that 'somewhat reasonable gains' statement would fit HL2, which is scaling with every gpu added but the benefit diminishes. cod is scaling almost optimal:gpus - max scaling - actual scaling
2gpu - 100% - 98%
3gpu - 50% - 44%
4gpu - 33% - 29%
RamarC - Thursday, February 21, 2008 - link
i'd like to see how it handles mismatched cards in 3/4 way configs. another site did a crossfire review with a hd 3870 paired with a hd 3850 and their combined performance approached a hd 3870x2.Bladen - Thursday, February 21, 2008 - link
I'll say.I am very surprised to see "unfinished" drivers and tech preforming almost optimally, albeit in only 1 test case.
I think AMD should heavily encourage Infinity Ward to licence out COD4's engine.
Griswold - Thursday, February 21, 2008 - link
"I think AMD should heavily encourage Infinity Ward to licence out COD4's engine."Oh please, no!
Samus - Thursday, February 21, 2008 - link
Yea, frak that. COD4's engine doesn't have the feeling or capability of the source engine, which scales great (except for the 4th GPU I suppose.)With more tweaking, the Source engine is most ideal. Obviously they shouldn't target Crytek's engine, though.