System memory to video memory bandwidth

What sort of bandwidth can you squeeze out from the system to the video
memory? Currently, my blits are reading 11 MB from the system memory and
writing 11 MB to the video memory every second (and 9 MB in fullscreen mode,
by the way, why is that lower?). Seems slow…

system specs:

K6-2 400 MHz
384 MB PC100 SDRAM
VIA VC3 Chipset
Voodoo 3 3000 AGP