The 1770 and 1772, which were 28-pin IC's intended for use only with 5-1/4"
drives, the primary difference between them being the step rates they
support, were not widely used. I have the 1770 on my AMPRO "Little Board"
but the numbers are out of sequence in the sense that the first of their
parts was the 1771, followed by the 179x series, with a shot at a 178x group
( intended to fill the gap with respect to M^2FM and (?) hard sectors )
which wasn't around long if at all. The 1791 was an inverted-bus version of
the 1793. This inverted bus was inherited from the1771, and was designed to
explout the benefit of the inverting bus' slightly shorter propagation
delays.
One advantage the 1770/72 offered was that they had drivers capable of
driving the 110-ohm terminated cable to the drives.
Shortly after they released the 1770/72, they started making boards for IBM
and compatibles, which either used all their production of the required
parts, or made them sufficiently unpopular with their former customers now
competitors that they stopped making these parts, among others. They did
make a couple of 765-compatible FDC's with cable-driving outputs which
appeared on some of their SCSI HDC's and their IBM-compatible boards.
I've only got one spare, and I'm hoping I don't need that. If you find
these, please let me know.
Dick
-----Original Message-----
From: Glenatacme_at_aol.com <Glenatacme_at_aol.com>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Sunday, September 26, 1999 8:26 PM
Subject: floppy controller IC (was Re: Fixing a PET?)
>In a message dated 09/25/1999 2:53:45 PM Eastern Daylight Time,
>CLASSICCMP_at_trailing-edge.com writes:
>
>Tony Duell wrote:
>> >Before that, most micros used off-the-shelf ICs. Although some of these
>> >chips are getting rather hard to find now -- some disk controllers
>> >(WD1771, Intel 8271, etc) are _very_ difficult to find new.
>>
>
>CLASSICCMP_at_trailing-edge.com replied:
>> Not all are that difficult - BG Micro ( http://www.bgmicro.com/ ), for
>> example, has a fairly decent selection of WD floppy controller chips.
>
>This looks like a pretty good source. However, they don't list the WD1770
>disk controller IC -- anyone know where these might be available?
>
>TIA,
>
>Glen Goodwin
>0/0
Received on Mon Sep 27 1999 - 12:32:25 BST