'My favorite platform' debate (was: Rack Mount Servers)

[Michael O'Donnell]

 [ This thread seems to indicate that the 'G'
   in GNHLUG actually stands for Geriatric... ]


>As for IBM and the 68K -- one of the initial PC specs
>was backward CP/M compatibility.  The 8088 seemed a
>logical choice to fulfill this unfulfilled "feature:"
>everything the 8080 was, and faster, to boot.

Those who ever wrote a CP/M program might appreciate
this trivia: you can "call 5' (the CP/M equivalanet
of a syscall) in a DOS program and it will actually
work because at offset 5 in the Program Segment
Prefix (PSP, a reserved area) they were careful
to code a jump to a jump to a wrapper routine that
would leap off into some undocumented DOS code that
eventually did something useful.  I believe that a
number of people had the notion that blind mechanical
translation of CP/M binaries into 8088 binaries would
be a less trautmatic way to transition customers onto
the new platform so they arranged for certain hax to
be introduced into DOS to support that.  And I think
there was also some effort to make some of the 8088
intruction formats, addressing modes and (damn them
for eternity on this one) register sets similar to
the 8080 to facilitate this same "migration path"...