On Sat, 14 Jul 2018, Grant Taylor via cctalk wrote:
I had a vague sense that different OSs had different types of floppy drives.
I've also heard of hard vs soft sector drives, but I have no idea what the
difference is.
The floppy disk has an "index" hole and sensor.
HARD sector disks have one hole per sector.
SOFT sector disks have only one hole, and divide the track into sectors in
software.
I'd used CP/M at school but assumed all CP/M machines used the same disk
format. Wrong!
*nod*
It's my understanding that MS-DOS was one of the earlier OSs to standardize
file systems used across disks for various computer manufacturers. There
were still some physical differences though.
CP/M DID have a "standard format" - 8 inch Single-dided, single density.
But, when manufacturers created double sided, and double density formats,
or used hardware that was not compatible with the "standard format", they
each came up with different ones. When 5.25" drives came out, each
format was different.
I estimate that there are 2500 floppy disk formats.
I once got an opportunity to talk to Gary Kildall. I asked him about
creating a standard format for 5.25" CP/M. He replied, "The standard
format is 8 inch single sided single density." I thought that maybe my
request wasn't clear, and suggested that it would be helpful if there were
also a 5.25" standard. He reiterated, "The standard format is 8 inch
single sided single density." Admittedly, a single standard was simpler
than having a single sided and a dounle sided standard, with single
density standard, and double density standard, for each size. (8 so far,
and no clear end in sight.)
The IBM PC domination of the market led to all of the imitators of IBM
being standardized. (5.25" MFM single and double sided, 8 sectors per
track and then 9 sectors per track. Then "High" density 5.25" (which was
basically similar to an 8"!). Then "720K" 3.5". Then "1.4M" 3.5". Then
"2.8M" 3.5".)
But, besides the IBM compatible MS-DOS, MANY companies had reasons for
other formats, even with MS-DOS, as well as CP/M.
That even included a few companies who simply deliberatly wanted
incompatability! Intertec (Superbrain) could not grasp any reason to
transfer files between their disks and others, other than attempts to
STEAL their "proprietary" software! (such as PIP.COM, FORMAT.COM, . . . )
They threatened to sue me if I included their formats in XenoCopy! That
was the first time that I added an additional format during a tradeshow.
But, MOST incompatabilities were for perceived advantages. Such as 800K
GCR on Sirius/Victor-9000. Or "quad density" 80 track formats, such as
720K.
Or 3.5", before IBM came up with one (PC-DOS 3.20). Companies that had
already implemented 3.5", such as Gavilan, scrambled to change their
formats to match IBM.
3 inch!
3.25 inch! (Dysan bet the company on the premise that software
availability would be the deciding factor on which "shirt-pocket" diskette
would win out. They created a surprisingly comprehensive publishing
project. Where are they NOW?)
NEC, however, made their "1.2M" format identical to their 8" format, and
then also made their HD 3.5" identical. (360RPM drive, instead of
the usual 300RPM) Although physically different, they all had the same
layout.
--
Grumpy Ol' Fred ci...@xenosoft.com
