Free NCR tower in Miami FL.

From: Richard Erlacher <>
Date: Wed Dec 8 12:32:35 1999

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


-----Original Message-----
From: Jeffrey l Kaneko <>
To: Discussion re-collecting of classic computers
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" <>
>> >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
>> 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
>> their 9224 chip. Unfortunately, by that time the patent on RLL
>> 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?
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Received on Wed Dec 08 1999 - 12:32:35 GMT

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