11 Oct
2008
11 Oct
'08
5:04 p.m.
On Sat, 11 Oct 2008, Chuck Guzis wrote:
We were plagued by customers simply changing diskettes
whenever they
felt like it. Relying on a checksum-after-select scheme such as that
used by CP/M and early MS-DOS versions was pretty ugly (and not at
all airtight, something that plagued MICROSO~1 no end).
Why didn't MICROS~1 ever document that the CPM ^C was fully enabled to
flush the disk buggers?
While
playing with the driver, I noted that the write
protect signal was
conditioned only on select, not on motor, head-load or ready.
Experimenting with some of the other engineers to see how fast one
could insert and remove a floppy gave a safe polling interval of
about 250 msec, which was barely noticeable in normal system
operation and performed only if there were open files on the drive.
Some of the single-sided 600 RPM Sony (0A1?) drives were also used in
a few CP/M systems, such as the Preis. It was a very noticeable
improvement over 5.25" media.
Cheers,
Chuck
--
Fred Cisin cisin at xenosoft.com
XenoSoft http://www.xenosoft.com
PO Box 1236 (510) 558-9366
Berkeley, CA 94701-1236