I am using either nForce of nForce2 internal graphics, and I see
warnings like this in my X log file:
Not using mode "1600x1200" (exceeds valid memory bandwidth usage)
Integrated graphics have stricter memory bandwidth limitations
that restrict the resolution and refresh rate of the modes you
request. To work around this, you can reduce the maximum refresh
rate by lowering the upper value of the "VertRefresh" range in the
Monitor section of your X config file. Though not recommended,
you can disable the memory bandwidth test with the "NoBandWidthTest"
X config file option.