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From: thau@h-sc1.UUCP (robert thau)
Newsgroups: net.arch
Subject: Re: What if IBM Had chosen the 68000?
Message-ID: <768@h-sc1.UUCP>
Date: Thu, 21-Nov-85 10:03:10 EST
Article-I.D.: h-sc1.768
Posted: Thu Nov 21 10:03:10 1985
Date-Received: Sat, 23-Nov-85 09:45:49 EST
References: <129@intelca.UUCP> <392@aum.UUCP> <225@l5.uucp> <533@scirtp.UUCP> <6139@utzoo.UUCP> <426@ecn-pc.UUCP> <427@ecn-pc.U <456@looking21 Nov 85 15:03:10 GMT
Organization: Harvard Univ. Science Center
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> 2) CP/M Software (8080) is given no place to migrate.  CP/M programs and
>    6502 programs all have a high degree of processor loyalty that C programs
>    for 16 bit CPU's don't.  You *can't* port a cp/m program to a 68000
>    without a total rewrite.  (This may be a good thing!)  What this means
>    is that CP/M doesn't die, and maintains strength the same way the Apple
>    ][ and Commodore Architectures hang on.  The result: CP/M and the 6502
>    are the only serious contenders against IBM.

WRONG.  Even the 8086 gave CP/M software no place to migrate.  It is true that
the register set-up is similar to that of the 8080.  However, the instruction
sets are not in one-to-one correspondance.  I recall a BYTE article several
years back which compared a few 8080-to-8086 translators which were on the
market at the time; all of them had to expand one instruction to three in some
cases, and many could be tricked into far worse.  There were the inevitable
problems with translation of operating system calls.  Lastly, any directly
translated software would be unable to use more than 64K bytes.

A bit of history:  one of the biggest problems with the IBM PC during its first
year out was that there was no software available.  In fact, somebody came out
with (of all things) an 8080 coprocessor board, called, I believe, Baby Blue,
so that people could run available CP/M software on otherwise useless big blue
paperweights.  If the chips really were *that* compatible, this never could
have flown.