how to read garden variety PC 360k floppies?

[eyaleb]

I can read the 1.2Mb ones just fine, but trying to read the 360k ones fails. I have no trouble reading with dd if=/dev/fd0 ....
Format ibm.360 produces many errors and garbage data.
ibm.scan produces many warnings but does extract the correct data.
Is there a cleaner way to do this?

I saw #180 (comment) but trying it produces screens-full of errors and it progresses VERY slowly. It retrieved only 2%. Surely there is a simpler way for such a common format?

GW V4 with fw 1.4, installed package is version 1.15.1.

TIA

[keirf]

Try adding option --dd=L to gw read. The drive probably needs to be informed of density via pin 2. This option will set pin 2 low (by default the pin is left high).

If dumping raw you may also want to try adding --adjust-speed=300 as the HD drive spins at 360rpm, but DD is normally at 300rpm. However most Greaseweazle --format= specifiers will auto-adjust for this.

[eyaleb]

This is also what the above linked discussion says, which I already tried to no avail.
I now tried reading in 4 ways

--format=ibm.360
--format=ibm.360 --dd=L
--format=ibm.360 --dd=H
--format=ibm.360 --adjust-speed=300

Got identical results. gw says it only found 18 sectors. Comparing to the good dd(*1) I see that the first 18 sectors are identical (so correct) but the rest is not. So gw reads the first track (both sides, 18 sectors) well but not further.

I then tried a second drive (Mitsumi D509V3) with similar failure. This drive has jumpers that can be adjusted (e.g. https://forum.vcfed.org/index.php?threads/floppy-drive-jumper-settings.56473/) but it works OK as is (with simple dd).

I kept the logs from the runs if it helps.
BTW, in case this matters, it should be clear that I am using Linux (hence dd). I do not have a Windows machine to test.

(*1) The disk contains a large zip file and the good dd copy tests and extracts OK so it is a valid reference.

[keirf]

An excerpt of the logs would have been helpful. I'm now pretty sure it must be full of "Ignoring unexpected sector" messages.

Probably you need to specify double-stepping as it's a 40t disk in an 80t drive. So add --tracks=step=2 to your command line. You may also still need --dd=L, you'll have to experiment.

[eyaleb]

Yes! using --format=ibm.360 --tracks=step=2 works, with both my drive and my friend's.
Adding --dd=L was not necessary but worked just as well.

Thanks.