5 Nov
1998
5 Nov
'98
3:29 p.m.
On Fri, 6 Nov 1998, Tony Duell wrote:
You are quite right, Tony. It was the 8089 I/O processor that I was
recalling. I guess that I erred in thinking that the 8089 was not a part
of the 8086 set.
- don
Do I not
recall correctly that the 8088 was in fact half of a two chip
set and that the 8086 was 'self contained', and that IBM elected to not use
the other half.
I don't know if you _recall_ it correctly, but I don't think it's correct.
You are possibly thinking of a couple of things, but they both apply to
the 8086 _and_ the 8088.
The 8086/8088 was designed as part of a chipset. The other members of the
chipset were the 8087 floating point processor and the 8089 I/O
processor. The latter was a very fancy intellegent DMA engine (and a lot
more). That was what IBM didn't use, alas - they used a kludge based on
the 8237 DMA controller from the 8080 family. Apricot did use the 8089 in
their machines, but, of course, thay weren't really IBM compatibles.
The other thing is that the 8086 and 8088 need an external clock
generator and bus controller. These were the same parts for both CPUs,
and IBM used them in the PC and XT.