On Sun, Apr 7, 2019 at 9:56 PM Mia Magnusson <mia_at_plea.se> wrote: > > Den Sat, 6 Apr 2019 17:37:27 +0200 skrev Francesco Messineo > <francesco.messineo_at_gmail.com>: > > Isn't the 1541C like a 1541 but with a track 0 sensor and changed ROM > to use that sensor? My impression were that this still used two 8kbyte > ROMs. Nope, I have all the versions and often repair them for other people. the only drives that have 2 x 8K ROMs are the long board and short board 1541. Schematic is available on zimmers.net if you like to check yourself. It's called 1541B. > IIRC the track 0 sensor interferes with the I/O ports required for the > IEEE-488 port. The linked description probably takes care of this, but > I'd advice to check what parts of the ROM does the track 0 check. If it > isn't in the same ROM as the IEEE/IEC code, then both ROMs needs to be > switched instead of only one of them. Not all the 1541C have a track-0 sensor, and anyway it's connected to PA0 of th 6522 that is a data line for IEEE-488, but since you need to add switches for port-B pins that have other functions in the IEC drive, you just add another logic (or analog, like CBM engineers would have done) on PA0 pin. > > While 1541-II is the new style case drive which indeed uses one 16kbyte > 27128. Yes, of course those use a single ROM too. Frank IZ8DWFReceived on 2020-05-29 21:42:30
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