Due to the recent surge of old software resources on the 'net, I've been downloading lots of Tandy (XT clone) software off web pages onto my Pentium, which has a 5.25" 1.2 MB drive, in the hopes of copying it to a 5.25" disk for transfer. Everybody knows that trying to write to a 360K disk in a 1.2MB drive usually works fine for the 1.2 MB drive, but then renders the disk mostly unusable for the 360K drive. (This is because the 1.2 MB drive is built for reading 80 tracks instead of 40, and the read/write head is narrower, which results in some residual "noise" left behind at the outer edges of each track that confuses the 360K drive's wider head.) This makes it frustrating to try to copy software over to the Tandy, since it's hit or miss whether or not you can actually read the data off the disk when you're done.
I've found a procedure to get around this that always works (at least, on my hardware): Bulk erase a low-density diskette, then low-level format it in the high-density drive. Detailed steps follow:
(The disk must be a standard double-sided double-density diskette for best results, instead of a high-density disk. You can usually tell if it's double-density by looking for a spindle reinforcement ring--that little ring of a sticker on the middle "hole" of the disk. If it has a ring, it's most likely double-density; if it doesn't, it's most likely high-density. This sounds like folklore, but over 95% of high-density disks don't have a reinforcement ring--look at your own disks next time and you'll see what I mean.)
format b: /4 /u
The /4 tells dos 6.22 to format the disk in the 1.2 MB drive for 360K (40 tracks (double-stepping), 9 sectors per track, sector size 512 bytes, two sectors to a cluster). The /u is undocumented depending on your version of DOS; it means "unconditionally format the disk without checking it first".
(Other versions of DOS's format and other format programs can probably do the exact same thing, and better; I have DOS 6.22, so that's what I'm reporting on.)
The 360K drive should read the disk perfectly. You might get lucky and be able to write to the disk from either drive repeatedly in the future and still be able to read it in the 360K drive, but this varies from disk to disk and drive to drive. I usually repeat the whole process for each disk's worth of info I need to transfer over, since bulking and formatting it only take about 45 seconds.
The 1.2 MB drive used to test this was a 3.5"/5.25" dual unit teac; the 360K drive is the original installed drive in my Tandy 1000 HD.
-- Jim Leonard (Trixter / Hornet) Email: firstname.lastname@example.org -- My ears burn: ------------------------------------------------------------- <Khyron> trixter is a mad crazy phat crackhead