All:
I?ve been busy lately rebuilding the floppy system on my IMSAI. I
scrapped the Frugal Floppy 8? in favor of a CompuPro Disk 1 using 5.25?
disks to emulate 8?. This has been a long running project, but with the
assistance from someone on comp.os.cpm who went through the exact same
process with nearly the same hardware, I?ve been able to create a brand new
CP/M 2.2 master disk. Yeah!
Anyway, one of the issues I have with the Teac FD-55GFR (1.2mb
high-density; no schematic) drives I?m using is that the motor runs all of
the time (just like an 8? drive) but these late-model Teac drives don?t have
head relays, so the heads are engaged all of the time.
I?m looking for some advice/whatever on engaging the motor when needed.
The Disk 1 is based on an 8272 controller chip and it has a HDL (head_load)
signal which, through jumpers can be made to appear on the *MOTOR signal pin
of the standard IBM floppy disk interface. I tested the HDL signal and it
activates at the right time, so its following the 8? sequence, but the pulse
width leads me to believe that it?s too short to let the motor spin-up and
go ?ready?.
There is a way to control this with software...and I may go that route
anyway...but has anyone done this sort of thing ? used a 5.25? HD drive to
simulate an 8? drive and if so, which drives did you use?
Any input appreciated. Thanks.
Rich
--
Rich Cini
Collector of Classic Computers
Build Master and lead engineer, Altair32 Emulator
http://www.altair32.com
http://highgate.comm.sfu.ca/~rcini/classiccmp