Tue, 11 Jul 2000 Norm Dresner wrote:
> At 05:14 PM 7/11/2000 +0200, David Olofson wrote:
> >Sat, 08 Jul 2000 Andrew Tuckey wrote:
> >[...]
>
> >x86 doesn't have DMA on the chip (*), but uses either the 8 DMA channels
> on the
> >mainboard chipset (4 x 8 bit + 4 x 16 bit; normally used with ISA boards)
> or PCI
> >busmaster DMA, which is supported by the PCI chipset but performed by the PCI
> >cards themselves. AGP is quite similar to PCI in this respect, AFAIK.
> >
> >(*) exception: some x86 clones for embedded systems, with some standard
> > chipset functionality included.
> >
>
> That's not quite correct: The Intel 80186/80188 had integrated DMA.
Yeah, I forget the 8018x! :-) IIRC, it was never user in a PC, but in varios
computer peripherals.
> What is (closer to being) correct is that no "PC's" were produced with an
> x86 CPU with integrated DMA --
I'm not so sure about that... There are these micro-AT integrated main boards
with all sorts of weird chips on them. I cant't remember seeing one with an
"MCU x86", but I wouldn't be surprized if they exist.
> indeed it could be argued that if a computer
> had integrated DMA, then it wasn't a PC-work-alike and hence not a "PC".
Disregarding that the chipset would look different, a PC with such a CPU could
still work like a PC, provided the DMA controller is compatible with that PC
standard thing. (Not that I would want to see that on any new hardware...!)
David Olofson
Programmer
Reologica Instruments AB
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