DMA transfer RAM-to-RAM

Question

A friend of mine has told me that on x86 architecture DMA controller can\'t transfer between two different RAM locations. It can only transfer between RAM and peripheral (such a

Answer 1

Yes, memory to memory transfer is possible well up to 80386 family I have tried with "modern" x86's :)

Specify RAM for source and destination. You might have to watch out for coherence of the L1 cache depending on the device you are programming and if you have enabled the cache.

You might find some code in the Linux kernel for refreshing video RAM pages in shadow memory. This rings a bell.