Install Floppies (Was: Compaq Deskpro boards/hard drives from

Chuck Guzis cclist at
Mon Jul 26 10:57:35 CDT 2021

The bottom line on floppy disks, in my view, is that they're a design
compromise out of late 1960s technology.

The platform (drive) is made to be inexpensive (for the time), as is the
media--all limited by, at best, early 1970s technology.  Back then,
almost all drive spindles were belt-driven and the small-format 5.25"
drives used DC motors with rather imprecise speed control. Issues such
as ISV (instantaneous speed variation) were rife, so the encoding and
decoding of information had to be very tolerant of speed anomalies.  In
addition, the media had to be interchanged between drives, which brings
up the hobgoblin of accurate track positioning.  Drives are essentially
"dumb" devices, so there's no provision for any sort of closed-loop system.

When I first ran across the things, I was amazed that it worked.  You
had a medium that could be interchanged between "dumb" drives, and it
was accessed with heads that contacted the surface of the disk.

Could we do better?   Absolutely, but the cost of the drive goes up.
Consider an early 1980s attempt by Drivetech (later sold to Kodak in a
bankruptcy sale).  192 track per inch with embedded servo, yielding, at
first, about 3MB per floppy, eventually going to 6MB.

The humble Zip disk (and the UHD disks) could get well more than 100 MB
on a floppy, using more state-of-the-art technologies.  Coatings have
improved considerably over time, but the humble floppy is still powdered
rust stuck to a plastic disc.

Curiously, the notion of a flexible disc dates well back to the 1950s,
when it was promoted for audio recordings that could be tucked into an
envelope and mailed.

The Zip disk was as close as we got to a universally-accepted candidate
for replacing the humble floppy drive.  However, it came too late.

The same story applies with alternate encoding technology.   For general
acceptance, MFM was pretty much the end of the line.   Earlier attempts
used group-code encoding.  Others used "zoned" recording to pack more
data on the outer cylinders than the inner ones.

But these all required the hardware peculiar to the system that created
the disks.  For all intents and purposes, the MFM 500KHz data rate
encoding was the end of the line.   Extended density media and drives
used a 1MHz data rate to get 2880Kb on a disk failed miserably.  The
barium-ferrite media was never cheap and the drives were not widespread.

I think it's remarkable when you think about it, that early 1970s 8"
floppies are still quite readable today.  I wonder if USB flash drives
will endure similarly.  We already know that stuff stored on the
Internet won't.


More information about the cctech mailing list