Pinout for SED9421 - test-drb@ccmp.vtda.org

28 Nov 2005

...
 From: "Allison" <ajp166 at
bellatlantic.net>

Subject: Re: Pinout for SED9421
   From: "Dwight K. Elvey" <dwight.elvey at amd.com>
   Date: Mon, 28 Nov 2005 10:46:28 -0800 (PST)
     To: cctalk at classiccmp.org
 From: "Allison" <ajp166 at
bellatlantic.net> 
 >   From: woodelf <bfranchuk at
jetnet.ab.ca> ---snip---

 Did anybody ever use a serial chip and a data
separater
rather than a floppy disk controler? 
Yes, many.  usually its a sync chip.
Allison 
Hi
 Besides the HeathKit hard sectored controller board,
used on both the H8 and the H89, Polymorphics also
used a serial chip to do data. In both of these
cases, as you state, they used synchronous serial
chips and not async. 
Err, Yes that's what I did say.  Sync chips were the norm 
Hi Allison
 I'm not contridicting, just pointing out some cases
to support. As I recall, the N* controller also used
the synchronous serial chip. I don't know of a case
that used a async part. All of these were used on
hard sectored disk.
 I don't know of any soft sectored that used serial
chips. I suspect that it is because these depended
on using illegal data clocking sequences in order
to mark sectors. This would require more external
circuits.
Dwight
...
 for brewed designs there were not OSI or done with TTL.
Often they were used because WD could not supply or was
not viewed as the desireable item due to lack of second
source (at least early on).  Some did it to have a
propritory format.
Allison