>
> I used to know that memory to memory copy is done by the DMA controller in
> the I/O bridge (Actually, this knowledge confues me because DMA controller
> normally does not store the data that pass through it. Now the source and
> destination are both memory, how can it achieve this at the same time with
> one memory bus?).
Almost nobody does memory-to-memory copy with DMA controllers. You
certainly don't do it on the PC.
> I was also told that the function bcopy() is used to
> setup DMA.
No, bcopy is used to move data from one place to another using the CPU.
> Now I look at the bcopy() function in i386/support.s, I only
> see instructions like "rep movsb". So how is the memory-to-memory copy
> done in FreeBSD?
With bcopy().
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