On Thu, 2005-03-10 at 16:29 -0600, Randy McLaughlin wrote:
I have a webpage describing disks and disk drives.
Yep - most useful it is too! :-)
Pin 2 on a 34 pin floppy connector is a little used
pin. It was used to
change the RPM on some 5.25" 1.2mb drives.
It changed the RPM from 360 RPM (pin 2 high) to 300 RPM (pin 2 low). This
was supposed to make it easier to read/write DD disks in a HD drive.
Only early AT controllers needed it, later controllers kept this pin high
and used an odd transfer rate.
Interesting. I'd always assumed that 1.2MB drives always changed the
speed too.
I was pondering earlier how much memory it'd take to buffer a whole raw
track of data; presumably the maximum would be a 1Mbps rate at 300rpm
rotation? (and say sample at 16x, plus store some form of clock info. It
still doesn't work out that bad).
I'm sure it must be possible to build some gadget that'll hang off a PC
parallel port and buffer data to local (static) RAM, allowing slower-
speed transfer to/from the host machine. Hopefully without needing
microprocessor control (i.e. bunch of RAM, few counters or something :-)
Maybe there's some reason it can't be done - otherwise I'd expect
someone would have done so by now! :-)
cheers
Jules