segmented memory models

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