> As a result, even for local graphics, the main cpu should be describing what it wants to be displayed and sending that description to the video card rather than just sending the image to be isplayed.
This, on a side note, is also why often when you're doing benchmarks of graphical toolkits the software rendering of X ends up being faster then the hardware accelerated version it's still advantageousness to use the GPU rendering IF you can do the majority of the rendering on the GPU. Certain toolkit microbenchmarks will often show that CPU rendering is faster in some things then GPU rendering. The GPU just sucks at certain things, but ideally you want to use the GPU 100% of the time to avoid the multiple trips over the PCI Express buss. Each time you have to send texture data across the buss your just burning hundreds of thousands of GPU and CPU cycles just waiting for data to be pushed over.
you can imagine the huge penalty you have if you do, say, text rendering in software, but do the rest on the GPU. Even if the GPU rendering was a dozen times slower, in the real world GPU will still win.
Luckily AMD and Intel are trying to simplify things quite a bit with putting CPUs and GPUs on the same hunk of silicon. No need to flush textures back and forth if your sharing the same memory. :) But even then making proper use of the GPU with software will yield huge improvements in efficiency and performance.