Test notes
We're sticking with our most recent suite of game tests here, so we have some basis for comparison. We've tested the Radeon HD 4890 OC and the GeForce GTX 275 with their very latest driver revisions, and we've included older results from a range of cards for comparison. In some cases, of course, the newer drivers could give our two stars today a bit of a performance advantage. Concentrate on the main comparison if you find that possible difference distracting.

I had hoped to test with a non-OC version of the Radeon HD 4890, as well, but we don't have such a card in our possession, and apparently the Overdrive feature in AMD's driver control panel doesn't support underclocking. I believe we could have accomplished our goals with a BIOS editor, but since this is a brand-new card and we were facing some time constraints, we decided to forgo testing at 850MHz for now.

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 i7-965 Extreme 3.2GHz
System bus QPI 4.8 GT/s (2.4GHz)
Motherboard Gigabyte EX58-UD5
BIOS revision F3
North bridge X58 IOH
South bridge ICH10R
Chipset drivers INF update 9.1.0.1007
Matrix Storage Manager 8.6.0.1007
Memory size 6GB (3 DIMMs)
Memory type Corsair Dominator TR3X6G1600C8D
DDR3 SDRAM at 1333MHz
CAS latency (CL) 8
RAS to CAS delay (tRCD) 8
RAS precharge (tRP) 8
Cycle time (tRAS) 24
Command rate 2T
Audio Integrated ICH10R/ALC889A
with Realtek 6.0.1.5745 drivers
Graphics
Asus EAH4850 TOP Radeon HD 4850 512MB PCIe
with Catalyst 8.12 (8.561.3-081217a-073402E) drivers
Dual Asus EAH4850 TOP Radeon HD 4850 512MB PCIe
with Catalyst 8.12 (8.561.3-081217a-073402E) drivers
Gigabyte Radeon HD 4850 1GB PCIe
with Catalyst 9.2 drivers
Visiontek Radeon HD 4870 512MB PCIe
with Catalyst 8.12 (8.561.3-081217a-073402E) drivers
Dual Visiontek Radeon HD 4870 512MB PCIe
with Catalyst 8.12 (8.561.3-081217a-073402E) drivers
Asus EAH4870 DK 1G Radeon HD 4870 1GB PCIe
with Catalyst 8.12 (8.561.3-081217a-073402E) drivers
Asus EAH4870 DK 1G Radeon HD 4870 1GB PCIe
+ Radeon HD 4870 1GB PCIe
with Catalyst 8.12 (8.561.3-081217a-073402E) drivers
Radeon HD 4890 OC 1GB PCIe
with Catalyst 8.592.1 drivers
Sapphire Radeon HD 4850 X2 2GB PCIe
with Catalyst 8.12 (8.561.3-081217a-073402E) drivers
Palit Revolution R700 Radeon HD 4870 X2 2GB PCIe
with Catalyst 8.12 (8.561.3-081217a-073402E) drivers
GeForce 9800 GTX+ 512MB PCIe
with ForceWare 180.84 drivers
Dual GeForce 9800 GTX+ 512MB PCIe
with ForceWare 180.84 drivers
Palit GeForce 9800 GX2 1GB PCIe
with ForceWare 180.84 drivers
EVGA GeForce GTS 250 Superclocked 1GB PCIe
with ForceWare 182.06 drivers
EVGA GeForce GTX 260 Core 216 896MB PCIe
with ForceWare 180.84 drivers
EVGA GeForce GTX 260 Core 216 896MB PCIe
+ Zotac GeForce GTX 260 (216 SPs) AMP²! Edition 896MB PCIe
with ForceWare 180.84 drivers
GeForce GTX 275 896MB PCIe
with ForceWare 185.63 drivers
XFX GeForce GTX 280 1GB PCIe
with ForceWare 180.84 drivers
GeForce GTX 285 1GB PCIe
with ForceWare 181.20 drivers
Dual GeForce GTX 285 1GB PCIe
with ForceWare 181.20 drivers
GeForce GTX 295 1.792GB PCIe
with ForceWare 181.20 drivers
Hard drive WD Caviar SE16 320GB SATA
OS Windows Vista Ultimate x64 Edition
OS updates Service Pack 1, DirectX November 2008 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.

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:

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.