Jan,
Folks on the list can correct me if I'm wrong, but Squeak heavily depends on doing bitblt's from memory to the screen buffer. The bitblt from memory to screen performance of a modern AGP based PC video card is as high as 200-300 megabytes/sec
Correct. There is one thing that's interesting as well and that's that blitting between VRAM directly is again quite a bit faster (since it doesn't need to go to the AGP bus - compared to the memory speed of a modern graphics card AGP is slow as hell ;-)
Some older display adapters had no way to map the screen buffer into memory and had to execute graphics processor commands that would take a stream of data written to an I/O port to get the bits to the screen.
This is exactly what an X-Server does (and the reason why using the XSHM extension for local display make such a difference on Unix Squeak).
Andreas