Re: Will IBM 360 Floppies work in Apple ][ Drives?

[dempson@actrix.gen.nz (David Empson)]

Paul Schlyter <pausch@saaf.se> wrote:

> In article <C-KdnaXNzue_10bYnZ2dnUVZ_riknZ2d@giganews.com>,
> Scott Alfter <scott@alfter.DIESPAMMERSDIE.us> wrote:
> >In article <1171893268.411041.183420@l53g2000cwa.googlegroups.com>,
> >KPR <krauer@rpmtec.com> wrote:
> >>Will IBM 360 Floppies work in Apple ][ Drives?
> >>
> >>I finnaly cleand up my basement and have about 400+  5 1/4 IMB 360k
> >>Floppies..
> >
> >At first, your subject line brought up the thought "floppies for a
> >System/360?"    Leaving off the "K" from "360K" had that effect.
> >
> >The weird thing is that I'm nowhere near old enough to have ever used one of
> >those beasts. :-) 
> 
> You should be happy for that!  :-)
> 
> >I suspect they never used floppy disks of any sort, let
> >alone 5.25" floppies.
> 
> Actually, the floppy was invented by IBM, back in the early 1970's.
> The first floppes were 8" floppies though, holding some 240 KBytes
> each (8" SSSD = Single Sided Single Density).

I used the standard IBM 8" SSSD floppy disks on a CP/M system in the mid
80s. If memory serves, it had 40 tracks, 32 sectors per track, 128 bytes
per sector, which would be 160 KB. Other systems might have used a more
efficient format with more bytes per sector (fewer gaps) and squeezed in
a little more per track, but I doubt they could have got 240 KB out of
it.

The same system supported DSDD 8" floppies, which used a double sided,
77 track, 17 sector, 512 byte format (1.3 MB).

The double density formats were highly variable and machine-specific,
but the SSSD 8" format was the official and original standard for
distribution of CP/M from Digital Research, and was intended to be used
as a cross-platform compatible format (as long as 8" drives were
available for that platform).

CP/M on an Apple II made things difficult by only using the Apple II
5.25" format, which meant software developers had to jump through some
hoops to get software onto the Apple II CP/M disks in the first place if
they were selling CP/M software for other systems.

The original transfer of the CP/M operating system to the Apple II
platform may have been done using an 8" disk drive and controller card.
Alternatively, DOS 3.3 might have been used as a go-between to copy the
OS and system applications from another platform.

After a working CP/M system was running on the Z80 card with a basic set
of tools, it would be possible to use serial ports to transfer other
files from a "standard" CP/M system, e.g. via XModem. The original
XModem implementation is ideally suited for transferring CP/M files, as
both use a 128 byte sector size and don't care about the exact number of
bytes in the file.

-- 
David Empson
dempson@actrix.gen.nz