4 floppy disk drives on a PC?

[Eric Smith]

Sellam wrote:
> Fred seems to be the Guru with regards to floppy formats, and perhaps I
> misinterpreted what I read, but I recall him bringing up a scenario in
> which a disk formatted as 360K on a newer drive would not be readable on
> an "actual" (i.e older) 360K drive, or the other way around, or something.

5.25-inch 1.2M "high-density" drives cannot reliably write to 360K disks
because of the narrow head gap.  They can't completely overwrite the
existing format or data, so when you try to read the results on a real
360K drive (or even on a 1.2M drive with slightly different alignment),
you aren't likely to be able to read it successfully.  In some cases you'll
read back the old data, because it still is present in two bands to the
sides of the narrow band of new data.

If you *must* do this, do it on an UNFORMATTED disk, i.e., one that was
never formatted, or one that's really been bulk-erased well (which is
hard to do).

Far better to use a 360K drive for that.

Fortunately the 3.5-inch drives commonly used on PCs are all 135 TPI
with the same head gap, so there's no problem with 1440K drives writing
720K disks.

Eric