Major performance hit w/reflections on ATI cards...why?

[moocat]

I run in a Nascar 2003 league. Many guys have run both Radeon and Nvidia cards with this sim and find that the ATI cards take a big performance hit when "reflections" on the car bodies is turned on but the Nvidia cards don't seem to care.

Can anyone tell me why this is? Is it a general shortcoming with any game that utilizes reflective surfaces or is it specific to Nascar 2k3?
This apparently has been an issue with this game through the entire Radeon line so I'm thinking it isn't a driver issue.

 

[otispunkmeyer]

isnt NASCAR 2003 an open GL game? i remember NASCAR Racing 4 was. My radeon 9500pro cant push that game as fast as my old gf3 or MX440 for that matter.

make sure you got it in Direct 3D mode, because when it comes to running OPEN GL, Nvidia really do whoop ATI's ass.

if its not that then i would guess that the game just prefers the way Nvidia's chips work

 

[otispunkmeyer]

ahhh i just remembered now, on my machine for some reason, if i ran D3D , i got the frame rate up nice and good, but it didnt look half as good as in OPEN GL mode, ATI just doesnt do OPEN GL to well