I don't know this for certain, but I was once persuaded that IBM had held
the patent on 2,7 RLL and let it expire in '83. There were, of course, lots
of other run-length-limited codes which would also have worked, but the 2,7
was so well documented and worked so well, that everyone jumped on the
bandwagon once it became available. Of course, WD came out with a chipset
that supported RLL almost right away, too.
They lost a lot of customers when they started making disk drives, though
they're a major player in that realm now. I guess it worked out OK for them
(WD).
Dick
-----Original Message-----
From: Jeffrey l Kaneko <jeff.kaneko(a)juno.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Wednesday, December 08, 1999 10:47 AM
Subject: Re: Free NCR tower in Miami FL.
On Wed, 8 Dec 1999 09:37:24 -0700 "Richard Erlacher" <edick(a)idcomm.com>
writes:
MFM disk
controller was made by NCR, but it looks like a 'cookbook'
design using the WD-100x chipset.
SMILE when you say that, pahdnuh! That cookbook design is what made
the microwinchester drive so simple to include that anyone with two
grey
cells and a little PLL knowledge could put
together a winchester
interface. That's why they became so cheap. It was the only way to do
your
own
controller at a competitive price for several
years, until SMC brought
out
their 9224 chip. Unfortunately, by that time the
patent on RLL
recording
had expired, so everybody wanted RLL.
Well, I merely wanted to state that while NCR 'rolled their own',
it really wasn't anything special. The wd-100x chipset certainly
was revolutionary, however. That meant almost anyone with a wire-wrap
tool and enough parts could interface a winchester to just about
anything (like say, a Xerox machine?). That was a major breakthrough
in 1981, but by 1984 (when my machine was built), it was pretty standard.
Who held the patent on RLL, and (consequently) lost their shirt
when it became standard on 'smart' disk drives?
Jeff
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