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.
