Try playing a DX10 game with the old nvidia card. The new cards are cooler than the old desktop nvidia cards. Drivers can certainly be an issue, as can the way the older games were written. Newer games that take advantage of the newer cards architecture should run faster. They are not replaceable as they are MXM boards with custom firmware.
PLEASE! Read the thread 2600xt?. You will be enlightened. I know its extremely long but you'll get it before the end.
I think that it was cheaper for Apple, and they thought that the iMac wasn't a gaming machine, it was more of a home office/multimedia center PC, and so the graphics didn't need to be top notch.
Actually, they do, and it is in the MBP: The 8600M. But yeah, you are right that DX10-class cards are almost all improvements in the shaders, rather than fillrate or polygon draw rate. Unified shader architecture, more shaders and geometry shaders are the bywords of DX10-class cards.All games out now are DX9, this card DX10. If Apple used a DX10 nVidia card, seeing they don't have a mobile card yet, we would still have the same problem.
DX10-class cards don't /need/ DX10 to work. They work just fine with DX9 (obviously)... and from the standpoint of the card, what level of DX they support only talks to what sort of minimum hardware is on the card. So to be DX10-class, a card must support shader model 4.0, and a couple other minor requirements.Plus what is the use to have a DX10 capable card when you need Windows Vista for it anyways!?
Well here you have actual framerates from 5 Mac games, vs. your one abstract benchmark. I know which evidence I will take as stronger.3D Mark has the Radeon 2600 which is in the iMac at 3500.
The GeForce 7600GT scores in the region of 3500 - 3600.
So to say the new card is a step down is not entirely accurate.