Classic != IBM AT

From: Don Maslin <donm_at_cts.com>
Date: Thu Nov 5 23:29:05 1998

On Fri, 6 Nov 1998, Tony Duell wrote:

> > 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.

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
Received on Thu Nov 05 1998 - 23:29:05 GMT