Mail Archives: djgpp/1998/02/23/09:01:31
Peter DOT Henn AT t-online DOT de (Peter) wrote:
> Hello PCI freaks,
> I want to read memory on a PCI adapter card as fast as possible.
> There is no problem to generate write burst on the PCI bus. The
> command "_movedatal" in the "sys/movedata.h" from the DJGPP compiler
> do this very fine and I see the burst on my LA. Also the PCI interface
> hardware can handle this easy save address-data pairs in a FIFO.
>
> But the problem is to read the PCI adapters memory (e.g. graphic
> card) from the CPU in PCI burst mode (or multiple read
> transactions).
> --> Where can I find an example C-code?
>
> If the CPU put a read command and the address on the PCI bus it will
> normally wait until it get the data from the PCI adapter. So possible
> I must access the PCI adapter memory in a CPU cached mode to generate
> burst transfers. Naturally the cache lines must be invalidated before to
> garantee cache coherence.
Peter: _movedatal doesn't make any special thing, it just uses the normal CPU
instructions. So I think that here is the PCI bridge the one that makes the
work so I don't know if you can write a generic code to get the maximun speed
in situations where the PCI chipset doesn't make it automagically.
Is just an opinion.
SET
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