🚀 go-pugleaf

>>Periodically people make reference to the "XOR" patent on this
>>and other groups. Are they referring to a couple of patents
>>held by the CADTRAK corporation that deal with issues such as
>>double-buffering, scrolling, video enlargement and cursor movement?
>
>I believe this (from prep.ai.mit.edu:/pub/lpf/patent-list) is the "XOR
>patent":
>
>  4,197,590
>  Method for dynamically viewing image elements stored in a random access
>  memory array
>  filed 1/19/78
>  granted 4/8/80
>  inventors Josef S. Sukonick; Gred J. Tilden
>  assignee NuGraphics, Inc.
>  Includes claims of "XOR feature permits part of the drawing to be moved or
>  'dragged' into place without erasing other parts of the drawing."
>  Twice upheld in court.  [Cadtrak now owns this?]

Yep. That's one of them. There are actually two. I looked around for
them last night but couldn't find them. If this is the dreaded "XOR"
patent, I'm a little confused as to why everyone is so worked up about
it. [I worked with these patents in Taiwan, in relative isolation 
from the computing community so I never heard them refered to as the
XOR patent(s).]

I do not think you will find any record of CADTRAK ever requesting a 
licensing fee from a software developer. The patent teaches an entire
computing device that includes a video subsystem that provides various
features by way of switching between banks of memory, superimposing
one region of memory over another (using XOR), or selectively displaying
sections of memory. To the best of my knowledge their enforcement efforts
are directed almost entirely against makers of *whole computing devices*.

I honestly can't say if these patents were "obvious" back in 1978. 
They are certainly obvious now, since they've been part of much-cloned
PC technology for over a decade. Remember, though, just how expensive
memory was back in the 70's. The idea of 1MB of memory (or even 256K)
on a video adapter would seem a tremendous extravagance. The CADTRAK
patents cover a variety of techniques for providing improved performance
for what was then a high-end graphics workstation.

Maybe this is like the camshaft example given earlier -- there's just no 
other sensible way to solve the problem. Maybe this particular 
patent is not contributing much to new innovation (last I heard, 
Sukonick was spending the bulk of his time living the Jimmy Buffet
lifestyle.) But this company *is not* dragging Random Q. Hacker out
of bed for using XOR in a GIF editor. And you *cannot* violate their
patents "in one line of code." To the best of my knowledge, they
haven't even gone after video adapter manufacturers for contributory
infringement (although I think some have licensed).

Now that I've said this, I would like to say that I am basically 
sympathetic to the goals of the FSF and the LPF. I think that there
are definitely some silly patents out there -- when I worked at
IBM I saw quite a lot of silly junk get patented. I think there is
a lot of room for software patent abuse in a system run by people
who are barely computer literate. But I don't think it serves your
cause well to consistently raise a boogeyman (or should that be
"boogeyperson" in these enlightened times?) that is simply not a
threat of either the type or virulence that your postings suggest.

doug

-- 
-----------                                                   -----------
douglas barnes                               Calgon can't take me away...
barnesdo@CS.ColoState.EDU                 From the things I did today -L7