Creating 5.25" floppies

Fred Cisin cisin at
Mon Aug 17 21:11:33 CDT 2015

>> NO.
>> Osborne SD was also single sided.
>> 10 256 byte sectors per track.  100K.
>> [IBM PC] "360K" was 9 512 byte sectors, with TWO sides used.

On Tue, 18 Aug 2015, Terry Stewart wrote:
> Hmm.  I don't have the machine in front of me to check (I'm at work), but I
> pretty sure my Osborne 1A drives are single sided not double sided.  But I
> have the double density modification so yes, around 180-200k per disk I
> imagine.   Using the PC and Imagedisk I could easy write DD single-sided
> disks in a double sided (360k PC) drive though.

I think that the Osborne DD was also single sided.
IF I remember correctly (unrefreshed dynamic wetware), it was 5 1024 byte 
sectors.  times 40 tracks, that would, indeed, be 200K.

"360K" is mainly just the NAME of a PC format of 9 * 512 * 40 *2 sides
The same diskette formatted for other machines could easily be anywhere 
from 87.5K (TRS80 SD only used 35 tracks) up to 400K,  or even less with 
some inefficient choices, or up to 800K at 96TPI, or even more with 
various strange choices, such as not having all sectors the same size.
Calling that diskette a "360K" provides a relatively unambiguous way to 
identify the 300 Oersted, 1M unformatted media, and the IBM PC 48tpi 
double sided floppy drive.
Yes, there are plenty of other further possible exceptions to keep some 
ambiguitiy in the terminology.

Grumpy Ol' Fred     		cisin at

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