>>>>> "Ty" == Ty Sarna <tsarna@endicor.com> writes:

Ty> In article <29126.820683482@NIAGARA.NECTAR.CS.CMU.EDU>,
Ty> <Chris_G_Demetriou@NIAGARA.NECTAR.CS.CMU.EDU> wrote:
>> It's not "would any", the correct question is "why wouldn't one."
>> _EVERY_ ISA DMA device driver, if "properly written" should work on
>> the i386 and the alpha (and other machines which support ISA, like
>> the amiga), with no #ifdefs.

Ty> Well, actually they wouldn't work on the Amiga, because for all of
Ty> the ISA bridges availible that I know of:

Maybe it's time for me to speak up now, as one who uses the ISA bus in
NetBSD/Amiga :-)

Ty is absolutely correct about DMA on the ISA side for the existing
dumb bridges.  It's just not possible.  However, in my framework, it's
also possible, but not implemented, to use one of the intelligent
bridges, like the x86 cards that attaches to both busses.  This would
be like using the x86 like an I/O controller, and would mean
controlling it via some virtual I/O protocol.  So there is a
possibility, however very small, that someone makes some code that
support ISA DMA on the Amy.  Of course, maybe someone does a new
bridge card with some dual-ported RAM to bounce DMA into, and a DMA
controller on board, who knows...

What the ISA-kit for Amiga supports today is thus only DMAless
devices, like com ports, lpt and ether, but, sad to say, the interrupt
performance is lousy, so high sped com ports don't really cut it yet.
Ether however is very nice to have.

Niklas

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