10 Sep
2023
10 Sep
'23
3:09 p.m.
On 9/10/23 07:35, Joshua Rice via cctalk wrote:
What confused me, is that i believe the 3.5" Sony
Microfloppy originally
had 70 tracks. I'm personally completely oblivious to any 40-track 3.5"
microfloppy formats.
I have a pair of Sony OA-D30V drives, which i believe were the first
commercially available 3.5" microfloppy drives, and they have a single
head. The format the machine that they're linked up to only uses 70
tracks (though the drives might be capable of a few more?) for a SSDD
format of 315KB.
40 track 3.5" microfloppy drives therefore seem more of a branching
derivative rather than the "predecessor" that the article seems to
allude to. Unless, of course, we're talking of an unrelated format that
just used the same size disks...
The early Sony Microfloppy is definitely not quite the standard "modern"
3.5" floppy disk we're aware of today, but is still largely compatible
with modern disks, with slight modification. Namely the drives have no
mechanism of opening the shutters, so i've found the easiest method is
taping the shutters on the disks open with a bit of sellotape.
Early Sonys were indeed 70 track, single-sided--and for several
versions, 600 RPM. A PC controller that can handle 3.5" HD floppies
will also handle the early Sony drives. I'm trying to recall if there
was a head-load solenoid in those also. I believe so.
There are 40 track derivatives; used for word processing, particularly
on some Brother models. No big deal; when reading those, one simply
double-steps a "normal" drive. In any case, as far as I recall, they
all used Brother's proprietary GCR encoding. I've processed a couple
hundred of those.
Brother WP drives are a bit unusual in that there's no track 0 sensor.
The drive simply bangs the head carriage against a stop and then
micro-steps to where it finds track 0 data. This creates a problem when
using "normal" 3.5" drives--I keep about 3 around with varying degrees
of misalignment to handle those.
Now, let's talk about 2.8" and 3.25" drives; UK readers are certainly
familiar with 3.0 inch CF drives used on Amstrads.
Then there are the oddball cases. Caleb UHD drives and 3M Superdisks...
--Chuck