Why not
simply hook up a 3.5" drive (DSHD is fine)? Get a DS2D
diskette by covering over the density aperture in a DSHD diskette and
format it up to 720K on your modern PeeCee using "format a: /n:9
/t:80". Write whatever you want to it and let the Commo read it.
The PC5
will not recognise a 3.5" disk, even using driver.sys to set the
parameters it always gives a "device
not ready" error.
Try masking off pin 34.