GoTEK SFR1M44-U100...

Fred Cisin cisin at
Sat Jul 14 18:47:16 CDT 2018

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 

>> 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 
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 

Grumpy Ol' Fred     		cisin at

More information about the cctech mailing list