From Newsgroup: comp.sys.cbm

Hi!

I'm just wondering why the old Commodore PET drives like the SFD-1001 are
able to store much more data than the Commodore 1541. Why did Commodore decrease the storage capacity from 1 MB to 170 KB when developing the 1541? Both the 1541 drive and the SFD-1001 drive uses 5 1/4" DS/DD floppy disks so
I don't see what the reason for this dramatic decrease in storage capacity
was. Was the way of storing data on the SFD-1001 perhaps not reliable since
the data density was too high? Was it perhaps much more expensive to produce
a drive that could store 1 MB per disk than one that could store 170 KB per disk? Did Commodore maybe want to sell more floppy disks so it was therefore they decreased the storage capacity? (There is an adapter so that an
SFD-1001 drive can be connected to a C64 and then much more data can be
stored on each floppy disk than with a 1541 drive.)

Best Regards,

Christian Johansson (change "combort" in my e-mail address to "comhem" if responding via e-mail)


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From Newsgroup: comp.sys.cbm

In article <USgSa.20869$dP1.39216@newsc.telia.net>,
Christian Johansson <c64@combort.se> wrote:

Both the 1541 drive and the SFD-1001 drive uses 5 1/4" DS/DD floppy disks so >I don't see what the reason for this dramatic decrease in storage capacity >was.

Well, the SFD-1001 and friends technically use DD/QD floppies: the track density is about twice as high, i.e., there are more tracks per side. At
the time DD media was certainly more common than QD media and there may have been concern about data reliability if people used DD media instead. Furthermore, the stepper motor and other mechanical components required to
make an 80-track drive may have been expensive. Remember that CBM usually designed stuff to be inexpensive.

--
David Evans (NeXTMail/MIME OK) dfevans@bbcr.uwaterloo.ca Ph.D. Candidate, Computer/Synth Junkie http://bbcr.uwaterloo.ca/~dfevans/ University of Waterloo "Default is the value selected by the composer Ontario, Canada overridden by your command." - Roland TR-707 Manual --- Synchronet 3.18b-Win32 NewsLink 1.113