24" Al iMac Benchmarks under XP SP2 not what they should be, any ideas why?

[Tinhead]

Hello community,

I'm a rather happy owned of a new Al 24" 2.4 iMac 2GB RAM. I saw RevToTheRedline's benchmarks on XP SP2 on the 2.8 iMac and my own benchmarks are considerably lower (even factoring in the difference in the CPU speed) than his. I have installed the Catalyst 7.11 drivers following his instructions.

Does anybody else get similar results to Rev's? Is there something wrong with the performance of my unit? I did see an increase in frame rates with the Catalyst drivers, around 25%, but still the values are low in comparison.

Thanks in advance.

Here are Rev's benchmarks:

Test system
24" iMac, 2.8Ghz Core 2 Duo Extreme, 2GB ram, 500GB WD, HD 2600 Series, Windows XP Pro SP2 all updates.

--ATI Catalyst 7.9.
Half-Life 2: Lost Coast (1920x1200, full HDR, max settings) 74.8fps avg
Counter Strike: Source (1920x1200, full HDR, max settings) 97.3fps avg
Doom 3 with FPS cap removed (1920x1200, ULTRA HIGH settings, 2x AA) 116fps avg, 88fps min
Unreal Tournament 2004 v3369 (1920x1200, max settings) 71fps avg
Americas Army v2.8.2 (1920x1200, max settings) 66fps avg

--Benchmarks with ATI Beta 8.0 Catalyst driver.
Enemy Territory Quake Wars (1440x900, max settings) 55fps avg
Bioshock (1440x900, max settings, DX9 mode) 35fps avg
CS Source (same settings as 7.9 driver) 100fps
GTR2 (1920x1200, everything at max) 85fps avg, 67fps min
Quake 3 Arena (1024x768, Default settings) 781fps avg
FutureMark 3DMark 2005 (defaults) 8694 marks
Unreal Tournament 2004 (same settings at 7.9 benchmark) 81fps avg (84fps avg in OSX version with 3369.2 patch)

--Games not benchmarked but run perfectly fine.
Company of Heroes at 1920x1200, max settings
Command & Conquer 3, 1440x900, max settings
AOE 3 on both Mac and PC, 1920x1200, max settings (runs much smoother in Windows though)
Battlefield 2142 (forced 1440x900, max settings)
Battlefield 2 (forced 1920x1200, max settings)
Half-Life 2: Episode 1 (1920x1200, max settings) I prefer to keep HDR off, it runs perfectly fine 60+ fps with it on, but I think HDR sometimes ruins the experience, call me crazy.