On 23 Jan 2007 at 19:30, Tony Duell wrote:
I still think they should have used the 8089 'I/O
coprocessor' which was
essentially a fancy DMA chip. That would have, for example, allowed DMA
transders to cross page bounadaries.
The 8089 was an odd duck, but the closest thing that Intel had going
to a smart channel processor.
IIRC, the 8089 had but two DMA channels, which migt have created some
problems seeing that the XT had 4 and the AT had 7. I would have
been delighted with something like an "82237" which would have given
24- or 32-bit contiguous addressability. Since the 80186 was already
in the works at that time, I imagine that Intel didn't feel any
particular pressing need to continute the IOP line.
It's my understanding that the 8089 went over like a lead dirigible.
I don't know of a single consumer-level product that used it.