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
