Re: 7664 and 1600x1200 (maximum pixel clock?)
The 7664 driver adds more "correct" mode validation checking of the pixel clock (the maximum pixel clock is indeed what is reported in the X log with 7664; the higher number reported in earlier driver versions is incorrect).
However, there is a bug that the mode validation is not properly taking into account reduced blanking, which will be employed when setting the mode. Reduced blanking is a technique for shrinking the blanking regions of a mode, resulting in a lower pixel clock.
This will be addressed in a future driver release, but the work around for 7664 is to add a 1600x1200 modeline with a low enough pixel clock to the Monitor section of your X config file. This one should be sufficient:
Modeline "1600x1200" 145.98 1600 1704 1872 2144 1200 1201 1204 1238 -HSync +Vsync
I apologize for the inconvenience.
NVIDIA Linux Graphics Driver Engineer