Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!execu!sequoia!rpp386!aubrey
From: aubrey@rpp386.cactus.org (Aubrey McIntosh)
Newsgroups: comp.arch
Subject: Re: Self-modifying code
Message-ID: <17132@rpp386.cactus.org>
Date: 13 Oct 89 15:49:56 GMT
References: <522@ryn.esg.dec.com> <1989Oct12.041940.5651@ginger.acc.com> <1989Oct12.162236.24239@utzoo.uucp>
Reply-To: aubrey@rpp386.UUCP (Aubrey McIntosh)
Organization: Big "D" Home for Wayward Hackers
Lines: 26

In article <1989Oct12.162236.24239@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes:
>In article <1989Oct12.041940.5651@ginger.acc.com> art@salt.acc.com (Art Berggreen) writes:
>>I seem to recall one of the primary paper tape bootstraps for PDP-11s
>>used a loop which read a byte from the tape into the instruction loop.
>
>Bootstraps written before the days of decent-sized EPROMs often employ
>all kinds of dirty tricks to minimize size.  The classic was the toggle-in
>(i.e. manually entered, none of this wimpy ROM business :-)) bootstrap

I'm beginning to believe that every time I have an original idea, there must
be a hundred people working on exactly the same thing.  In my case, there
was a pdp8e connected to a mass spec, and a 16 bit machine in another
building that had the loadable programs.

When a comm packet of type 'execute there' passed its checksum,
the 'go loop' instruction was overwritten with the (successfully)
loaded code's start up address.  Saved lots of walking across campus
to re-toggle after a comm error. 



-- 
Aubrey McIntosh                  Freelance using Modula-2
                                 Real time, embedded, instruments.
Austin, TX 78723                 Enquiries welcome
1-(512)-452-1540                 aubrey%rpp386.Cactus.org@cs.utexas.edu