Looking for an 8 bit FDC...

Chuck Guzis cclist at sydex.com
Tue Oct 25 16:44:43 CDT 2005


On 10/25/2005 at 1:46 PM Fred Cisin wrote:

>The IAM interval is easily handled by masking that signal.  (interrupt the
>cable, or (on older cruder drives) cover the index with tape.)

I did better than that--I inserted a flip-flop and a gate to optionally
pass the index signal every OTHER rev.   But why do it if you don't have
to?

>I have half a dozen formats that I was unable to put into XenoCopy,
>due to 128 MFM.  I never could get reliable reading, so I did those with
>a 1791.

I believe that Don Maslin discovered that any adapter with a National 8473
would do the trick (but not the 8477, strangely enough).

Whatever, stay away from the Intel 82077AA-1 chips--they cannot write FM.
When I asked an Intel application engineer about why Intel broke this
capability (the 82077 could do the write), his answer was "who writes FM
diskettes anymore?".  You see this kind of thinking in the current crop of
USB floppies.

>I don't remember any non-standard address marks other than Tandy, but
>there could have been.
>'course the 1791 didn't want to write all of the ones that the 1771 did!

I'd have to dig through my notes, but there were a few others.   I've got a
couple WD 1781's here; I take it that they're a pretty rare bird...

>I understand that the 765 multi-sector "track read" was better for MOST of
>the market, but WE would rather have had the WD style "raw" track read.

No kidding. 

Has anyone ever used the Signetics 8x330 bit-slice floppy controller?  Like
most of the 8x300 line, a very strange bird.

Cheers,
Chuck





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