segmented memory models

[Chuck Guzis]

On 2 Aug 2008 at 17:18, Fred Cisin wrote:

> Were either the 5150 or the 8086 architecture intended to last until 1990?

I don't think the 8086 was intended to last until 1983.  I can 
remember asking our Intel sales engineer about using the 8086 
sometime around 1979.  His response was to wait for the Real Deal--
the iAPX432/8800.  At about that time, we were starting to get early 
data and then steppings of the 80186 and decided to use that chip 
instead of the 8086, the '186 being more advanced and faster than the 
8086.  We included a socket for the 80286, even though real working 
(i.e. protected mode running) software (Xenix) wasn't ready by any 
stretch at the time (the port of Xenix to the 80286 was a joint 
Microsoft/Intel deal, with Intel doing the kernel work).  Both the 
80186 and 80286 were ceramic LCC package and ran at 6 MHz.  What was 
surprising is that no IBM PC product ever used the 80186.

I recall a bug in the early 186 steppings that damned near drove me 
nuts (or maybe it actually did).  We'd have a system running that 
would seemingly crash at random every other day or so.  Being an 
early stepping, there was no ICE for the thing and with the on-chip 
peripherals, there weren't a lot of places to hang a logic analyzer. 
You'd write some diagnostic code and it'd run flawlessly for a week.

Eventually, it turned out that what was happening was that the  SI 
and DI registers would get clobbered by DMA activity.  After much 
lost hair, we discovered the problem, and phoned the Intel 
application engineer assigned to the 80186.  He told us, that yup, 
they knew about it--had for a week.  Just never bothered to tell 
anyone about it.

A month out of my life that I don't miss at all.

If you haven't yet, by all means research the 432--the architecture 
is about as far from the 8080/8086 family as one could get.  Perhaps 
a picture of what the PC (at least the advanced models) might have 
been.

Cheers,
Chuck