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From: bdietz@sdcc13.ucsd.edu (Jack Dietz)
Newsgroups: sci.space.shuttle
Subject: Re: New Shuttle Computers
Summary: Shuttle language, address space
Message-ID: <17412@sdcc6.ucsd.edu>
Date: 12 Mar 91 11:34:56 GMT
References: <1991Mar10.164459.5216@rodan.acs.syr.edu> <1991Mar10.210059.26743@nowhere.uucp> <1991Mar11.200136.7329@casbah.acns.nwu.edu>
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As I recall from the very early flights and a dog-eared copy of the
Space Shuttle Operator's Manual, the original shuttle programs were
written in Very High-level Shuttle Instruction Code (VHSIC).  This
came up during those T-00:31 launch aborts when the announcers were
trying to cover programmers frantically debugging on national
television...

Also, in the instructions from the SSOM, several times during the
launch sequence the instructions tell the commander to punch in a
command to load another software package.  [OPS] 105, for example,
loaded the package used between T-19 minutes and T-5 minutes, I
believe.

A suggestion: If the instruction space is limited to 128K words or
so, bank switching sounds like an answer -- copying the routines
directly to ROM images with an added instruction to switch banks at
the end of each.

Howabout a milspec SPARC processor?  (just kidding)  Actually, the
XT-370 computers which IBM made for a while used a 68000 with the
microcode replaced to run 370 programs on an expander card.  Perhaps
NASA could convince a couple of companies to update that chip in a
radiation-hardened manner?
--
The Army Axiom:                       | Jack Dietz (bdietz@ucsd.edu)
  Any order that can be misunderstood | Looking Forward to a Future
  has been misunderstood.             |     without Bellamyites
--
Segal's Law:                                         | Jack Dietz
  A man with one watch always knows what time it is. | (bdietz@ucsd.edu)
  A man with two watches is never sure.              | Engineer-To-Be