Test notes
CrossFire X presents a wealth of possible test configs, but we chose a couple that we thought would be representative of common configurations. For our quad-GPU tests, we used a pair of Radeon HD 3870 X2 cards, and for three GPUs, we used a single Radeon HD 3870 X2 paired with a Radeon HD 3870. Our test motherboard, a Gigabyte GA-X38-DQ6, has two PCIe x16 slots with a full 16 lanes of PCIe 2.0 connectivity routed to each. These hardware combinations should be more or less optimal for CrossFire X in terms of interconnect bandwidth and the like, giving it plenty of opportunity for performance scaling.
Please note that we tested the single and dual-GPU Radeon configs with the Catalyst 8.2 drivers, simply because we didn't have enough time to re-test everything with Cat 8.3. The one exception is Crysis, where we tested single- and dual-GPU Radeons with AMD's 8.451-2-080123a drivers, which include many of the same application-specific tweaks that the final Catalyst 8.3 drivers do.
Our testing methods
As ever, we did our best to deliver clean benchmark numbers. Tests were run at least three times, and the results were averaged.
Our test systems were configured like so:
| Processor | Core 2 Extreme X6800 2.93GHz | Core 2 Extreme X6800 2.93GHz |
| System bus | 1066MHz (266MHz quad-pumped) | 1066MHz (266MHz quad-pumped) |
| Motherboard | Gigabyte GA-X38-DQ6 | XFX nForce 680i SLI |
| BIOS revision | F7 | P31 |
| North bridge | X38 MCH | nForce 680i SLI SPP |
| South bridge | ICH9R | nForce 680i SLI MCP |
| Chipset drivers | INF
update 8.3.1.1009 Matrix Storage Manager 7.8 |
ForceWare 15.08 |
| Memory size | 4GB (4 DIMMs) | 4GB (4 DIMMs) |
| Memory type | 2
x Corsair
TWIN2X20488500C5D DDR2 SDRAM at 800MHz |
2
x Corsair
TWIN2X20488500C5D DDR2 SDRAM at 800MHz |
| CAS latency (CL) | 4 | 4 |
| RAS to CAS delay (tRCD) | 4 | 4 |
| RAS precharge (tRP) | 4 | 4 |
| Cycle time (tRAS) | 18 | 18 |
| Command rate | 2T | 2T |
| Audio | Integrated
ICH9R/ALC889A with RealTek 6.0.1.5497 drivers |
Integrated
nForce 680i SLI/ALC850 with RealTek 6.0.1.5497 drivers |
| Graphics |
Diamond Radeon HD
3850 512MB PCIe with Catalyst 8.2 drivers |
Dual
GeForce
8800 GT 512MB PCIe with ForceWare 169.28 drivers |
|
Dual Radeon HD
3850 512MB PCIe with Catalyst 8.2 drivers |
Dual
Palit GeForce
9600 GT 512MB PCIe with ForceWare 174.12 drivers |
|
|
Radeon HD 3870 512MB PCIe with Catalyst 8.2 drivers |
||
| Dual
Radeon HD 3870 512MB PCIe with Catalyst 8.2 drivers |
||
|
Radeon HD 3870 X2 1GB PCIe with Catalyst 8.2 drivers |
||
|
Dual Radeon HD 3870 X2 1GB PCIe with Catalyst 8.3 drivers |
||
|
Radeon HD 3870 X2 1GB PCIe + Radeon HD 3870 512MB PCIe with Catalyst 8.3 drivers |
||
| Palit
GeForce
9600 GT 512MB PCIe with ForceWare 174.12 drivers |
||
| GeForce
8800 GT 512MB PCIe with ForceWare 169.28 drivers |
||
| EVGA
GeForce 8800 GTS 512MB PCIe with ForceWare 169.28 drivers |
||
| GeForce
8800 Ultra 768MB PCIe with ForceWare 169.28 drivers |
||
| Hard drive | WD Caviar SE16 320GB SATA | |
| OS | Windows Vista Ultimate x86 Edition | |
| OS updates | KB936710, KB938194, KB938979, KB940105, KB945149, DirectX November 2007 Update | |
Thanks to Corsair for providing us with memory for our testing. Their quality, service, and support are easily superior to no-name DIMMs.
Our test systems were powered by PC Power & Cooling Silencer 750W power supply units. The Silencer 750W was a runaway Editor's Choice winner in our epic 11-way power supply roundup, so it seemed like a fitting choice for our test rigs. Thanks to OCZ for providing these units for our use in testing.
Unless otherwise specified, image quality settings for the graphics cards were left at the control panel defaults. Vertical refresh sync (vsync) was disabled for all tests.
We used the following versions of our test applications:
- Call of Duty 4: Modern Warfare 1.4
- Crysis 1.1
- Half-Life 2 Episode Two
- Unreal Tournament 3 1.1
- 3DMark06 1.1.0
- FRAPS 2.9.4
The tests and methods we employ are generally publicly available and reproducible. If you have questions about our methods, hit our forums to talk with us about them.
