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Subjectspecific optimizations for unaccelerated framebuffers
  Just a question:

Has anybody ever tried to have a copy of the video memory in the main
memory. All the software would access the copy in main memory, and
the standart DMA is used (permanently) to update the real video memory.
Maybe a 32 bit int could be used to skip unmodified 64K pages (1 bit
per page).
The main processor would never have to wait for PCI read/writes.

In fact the question is: what kind of bandwidth can we have from a
standart PC DMA (memory to memory copy)?
The other problem could be the addresses limits, but using the VESA1
interface (window switching at 0xA0000), the video memory image
below 16 Mb and known I/O ports (see Gujin) would solve that.

Someone has bandwidth measures?

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