Path: utzoo!utgpu!attcan!uunet!husc6!cmcl2!rutgers!gatech!ncsuvx!ece-csc!mcnc!ecsvax!urjlew
From: urjlew@ecsvax.uncecs.edu (Rostyk Lewyckyj)
Newsgroups: comp.arch
Subject: Re: Split I and D caches and IBM lawyers
Message-ID: <5536@ecsvax.uncecs.edu>
Date: 4 Aug 88 23:24:45 GMT
References: <62370@sun.uucp> <15086@apple.Apple.COM> <62555@sun.uucp> <15129@apple.Apple.COM>
Organization: UNC Educational Computing Service
Lines: 39


Mr. Baum claims that Ppabiggness does not provide an advantage
in patenting and patents. He also seems to feel that because
IBM managed to get a patent on a precise implementation of
a perhaps common art technique,  it must have been an
innovation.
Well I disagree with thatose opinions.
Big companies have staff lawyers to put together the paperwork
to claim even small "innovations", and they do this almost as
a matter of course. A small complany ofr individual will not
often do this. First because he may think the innovation too
trivial. Second because of the expense and the knowledge that
he can not defend the patent if it is infringed.
As regards to sothe specifics of "setting the dirty cache bit
under software contorlrol in a split I and D cache machine".
Ever since there were different memory hierarchies there
have been caches. (Read a matrix in from tape, then write it
out. etc). Initially these theings were very much under an
individual proggrammers control. (eg getting Swords from backing
store on a CDC). Then some people worked very hard to try and
do this kind of fetching of data to the faster storage (cache)
automatic and transparent to the user. I have heard that IBM
specifically Dr. Blauwe (sp?) made this possible on the 360s
with the Blauwe box (ref. Computer architecture class taught
by Dr. Fred Brooks). So it is not surprising that people were
mainly thinking of caches as transparent to the programmer.
HOwever the logic to check on the validity of the cache had
to be there in a harware program. And allowing programmer
control of the dirty bit flag is simply going back to when
the programmer did it all himself. What IBM did is implement
a specific instance of something that needs to be done to make
caching work, and happened to patent it because they try to
patent everything. NOw they are trying to wield the patent 
as a club.
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  Reply-To:  Rostyslaw Jarema Lewyckyj
             urjlew@ecsvax.UUCP ,  urjlew@tucc.bitnet
       or    urjlew@tucc.tucc.edu    (ARPA,SURA,NSF etc. internet)
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