> On Jan 17, 2021, at 2:12 PM, Fred Cisin via cctalk <[email protected]>
> wrote:
>
> On Sun, 17 Jan 2021, Paul Koning via cctalk wrote:
>> 2. RD50s are odd; they use pin 32, which is normally drive select 4, as an
>> output to indicate "I am an RD50". The software looks for that signal. So
>> to emulate an RD50, install the jumper for drive select 4 (alongside the one
>> for drive select 1) on P7.
>
> Unimportant NIT:
> On most drives, pin 32 is side select.
>
> On TRS80 [Model 1], which had single sided drives, pin 32 was the fourth
> drive select. (10, 12, 14, 32) The cable connectors had missing pins for
> three of those four, and the drive was jumpered to respond to all four. Using
> four drives AND adding double sided support required some modifications.
>
> But, on most machines after that, pin 32 is SIDE SELECT. It is used to
> access side B of the drive.
You seem to be talking about floppy drives. The MFM emulator deals with hard
drives, and the RD50 I mentioned is a hard drive (sold by DEC, 5 MB, the
original hard drive for the PDP-11 base Professional series).
paul
