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From: peterh@tekgvs.UUCP (Peter Hildebrandt)
Newsgroups: net.graphics
Subject: Re: exclusive-ORed cursors
Message-ID: <1238@tekgvs.UUCP>
Date: Fri, 4-Oct-85 14:20:19 EDT
Article-I.D.: tekgvs.1238
Posted: Fri Oct  4 14:20:19 1985
Date-Received: Sun, 6-Oct-85 14:38:01 EDT
References: <588@stc-b.stc.UUCP> <5988@utzoo.UUCP> <914@turtlevax.UUCP> <745@terak.UUCP>
Reply-To: peterh@tekgvs.UUCP (Peter Hildebrandt)
Organization: Tektronix, Beaverton OR
Lines: 23
Summary: The patent does exist. 

>
>The use of exclusive-OR to draw and erase cursors, rubber band lines,
>etc. is covered by patent number 4,197,590.  The holders of that patent
>are, um, "aggressive" about defending their patent.
>
>Nearly as I can tell, the company that holds that patent produces no
>products; its only income is from license fees on that patent.
>
>Doug Pardee -- CalComp -- {calcom1,savax,seismo,decvax,ihnp4}!terak!doug

Yes, there is in fact a patent on the exclusive-or for cursors.  The person
who holds the patent actively seeks out companies using graphics controller
chips with the feature (like the NEC 7220 or the Hitachi 63484).  While I
was at Vectrix Corportaion, we were approached by the patent holder who 
demanded royalties.  We, too, could not believe he had actually gotten a
patent on a mathematical process.  But after he told us he only wanted a flat
fee (as I recall) of around $100 or $200, we couldn't refuse.  Who can afford
to fight a legal battle over $100?  What a neat way to make money.  If he makes
$100 on 100 companies, he has just earned $10,000 for nothing. 


		Peter Hildebrandt
		Tektronix Laboratories


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