Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!ut-emx!nather
From: nather@ut-emx.UUCP (Ed Nather)
Newsgroups: comp.arch
Subject: Re: WISC "impossibility"
Message-ID: <12831@ut-emx.UUCP>
Date: 6 May 89 16:02:26 GMT
References: <38853@bbn.COM> <423@bnr-fos.UUCP> <288@ctycal.UUCP> <1140@ptolemy.arc.nasa.gov>
Organization: The University of Texas at Austin, Austin, Texas
Lines: 27

In article <1140@ptolemy.arc.nasa.gov>, raymond@ptolemy.arc.nasa.gov (Eric A. Raymond) writes:
> >A couple of years ago there was an article in Byte about a proposed design
> >which they called WISC for Writeable Instruction Set Computer.  The idea
> 
> Am I missing something?  Wouldn't a machine with loadable microcode
> satisfy this?  Hasn't that been done for years (and was was the floppy
> disk was designed to store)?  Even LISPM's have it.
> 
> Did the original poster mean that a program could change the ucode?
> This is a little more complicated ....
> 

The first "WISC" machine I know of was designed about 1959.  It used
non-destructive magnetic cores to hold vertical microcode, which could,
in fact, be changed by an operating "program" that was in execution.
The idea was to be able to emulate different computers at the machine
instruction level, and be able to use an instruction set tailored for
writing compilers to write them in, and a different instruction set to
execute the generated code.  All the machine "instructions" were just
microcode subroutines.  The machine  (the PB440 by Packard Bell Computer)
never made it to market, but a prototype worked as advertised.



-- 
Ed Nather
Astronomy Dept, U of Texas @ Austin