Question on IBM JX floppy disks

[krebizfan]

I have been working with a number of older disk formats and researching some other formats just to find out what I won't be able to read. The IBM JX in its earlier configuration had drives described as 360kB 3.5" but how the disks were formatted differs in the accounts I have read. I don't need to find out this out since I don't have JX disks and am unlikely to encounter an IBM JX but I am still curious.

Was the 360kB JX disk format single-sided, double-sided using the first 40 tracks, double-sided using 40 tracks but skipping every other track, or some other format I have not read about?

 

[Chuck(G)]

Used only the first 40 cylinders (looked like a 360K 5.25" drive), but there was a later BIOS upgrade to allow use of all 80 cylinders.

Tezz probably knows where there are a couple of these in his neck of the woods, but there's a lot of water between here and there.

 

[krebizfan]

Thank you.