Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!indri!lll-winken!uunet!mfci!rodman
From: rodman@mfci.UUCP (Paul Rodman)
Newsgroups: comp.arch
Subject: WISC "impossibility"
Message-ID: <831@m3.mfci.UUCP>
Date: 5 May 89 21:16:12 GMT
References: <38853@bbn.COM> <423@bnr-fos.UUCP> <288@ctycal.UUCP> <1262@l.cc.purdue.edu> <231@celit.UUCP> <10544@cit-vax.Caltech.Edu> <27034@ism780c.isc.com>
Sender: rodman@mfci.UUCP
Reply-To: rodman@mfci.UUCP (Paul Rodman)
Organization: Multiflow Computer Inc., Branford Ct. 06405
Lines: 32

In article <27034@ism780c.isc.com> marv@ism780.UUCP (Marvin Rubenstein) writes:
>In article <10544@cit-vax.Caltech.Edu> yair@tybalt.caltech.edu.UUCP (Yair Zadik) 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
>
>Yes, it is a bad idea.  In the mid 60's I was at Standard Computer (no longer
>in existance) and I actually built such a machine.  It was called the
>
>In practice we found that it was impossible to make the thing work because
>any modification to the control store could effect th 'basic' instruction
>behavior.  As an example, one of the problems we found was that when running
>the 'FORTRAN' instructions, double precision floating divide produced the
>wrong answer if the instruction was executed at the same time as a tape unit
>was reading a file mark.  I decided that there was no way to support a
>machine like that in the field, so the experment was terminated.
>

So you had a bad design....why does that make it a bad idea? I personally 
think that a VLIW with  Henry's "interpreter" posting idea does the job quite nicely,
however idea isn't "impossible".

I sounds to me like you just had a poorly thought out design. I see no reason
for building a machine that gets floating point errors when encountering a
file mark (?!??)...that is just plain *broken* design.

>   Marv Rubinstein


    Paul K. Rodman 
    rodman@mfci.uucp
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