Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hpvcfs1!johne
From: johne@hpvcfs1.HP.COM (John Eaton)
Newsgroups: comp.sys.ibm.pc
Subject: Re: re 640K limit
Message-ID: <21990004@hpvcfs1.HP.COM>
Date: 23 Jan 90 22:21:33 GMT
References: <4668.25aed7f2@uwovax.uwo.ca>
Organization: Hewlett Packard, Vancouver, WA
Lines: 28

<<<<
$How would things have worked out if IBM had put this 384k block at the bottom
$of the memory (0-384). That would have left no constrictions on upward
$expansion except the 8088. And that problem would have been remedied by
$the 80286.		-ted-
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You still need 1K of RAM at 0000:0000 for the Interrupt vector table.

They might have had an easier time expanding if they had allowed for
other processors with differing sizes of segments. Instead of fixing
it at 4 bits you could have gone to 5,6,7 etc.


In order to understand some of the limitations of the PC you must remember
how the 8086 came to be. Intel was on a roll with the 4004/8008/8080 and
decided to go all out and design a micro that really had some POWER. It
was to be something that could challenge the minis and become the chip
of the 80's. I believe it was originally called the "432". But they still
needed to keep business coming in the door until this wonder chip was ready
so they decided to do a quick and dirty enhancement of the 8080. This was the
8086. It's only purpose was to keep the 8080 family alive until Intel could
deliver its real processor. Its hard to fault the designers for any design
decisions that were appropriate for it's expected lifespan.

John Eaton
!hpvcfs1!johne