Update on SA-800 Problem

Jay Jaeger cube1 at charter.net
Sat Aug 22 09:26:03 CDT 2015

On 8/22/2015 12:20 AM, Chuck Guzis wrote:

> On 08/21/2015 06:46 PM, Jay Jaeger wrote:
>> One other thing I have noticed is that sometimes after a read problem
>> on the bad drive the FD 1791 floppy controller chip seems to get into
>> a "snit" that even a reset does not cure - I have to cycle power to
>> get it back.  Now that I have a reliable drive as the first drive, it
>> is clear that this is not a reinsertion / wobble issue.  So, I will
>> have to check the reset line going to that and the PIO chip that
>> supports it to see if there is a problem on the board.  I also have
>> some spare FD 1791's I can try, that are of a slightly later
>> revision, to see if the problem is related to that specific chip.
> Try a later revision of the 91.  We had miserable problems with the
> WD1781 (the FDC that no one has heard of) and eventually had to
> incorporate an external register bit into the design to enable software
> to do a "hard" reset of the 1781.  It could occasionally just go deaf
> and dumb; WDC knew about the problem and that was the only solution
> offered.
> --Chuck

Yes, my thought as well.

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