Article View: comp.arch
Article #2693Re: Self-modifying code (really bootstraps)
From: David Collier-Brown
Date: Thu, 19 Oct 1989 11:58
Date: Thu, 19 Oct 1989 11:58
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The ICL System 10 had an interesting boot (which used no self-modifying
code whatsoever (:-)). Zero, as an instruction, was interpreted as
opcode operand modifier
====== ======= ========
disk_load address_0,sector_0
and was generated when one cleared the screen (!) and pressed the execute-
immediate button.
Poof! The bootstrap appears.
This was less desirable when someone tried to execute data, of course,
but did show a fine bit of subtlety in assigning opcodes.
--dave
--
David Collier-Brown, | davecb@yunexus, ...!yunexus!davecb or
72 Abitibi Ave., | {toronto area...}lethe!dave
Willowdale, Ontario, | Joyce C-B:
CANADA. 416-223-8968 | He's so smart he's dumb.
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Path: arc1-ca.pugleaf.net!utzoo!yunexus!davecb From: davecb@yunexus.UUCP (David Collier-Brown) Newsgroups: comp.arch Subject: Re: Self-modifying code (really bootstraps) Message-ID: <4465@yunexus.UUCP> Date: 19 Oct 89 11:58:43 GMT Article-I.D.: yunexus.4465 References: <6481@pt.cs.cmu.edu> <9175@etana.tut.fi> <672@sce.carleton.ca> <JTHOMAS.89Oct18152705@tecate.nmsu.edu> Organization: York U. Computing Services Lines: 22