Would make sense, at least in principle. In CBM DOS, 'unit' actually refers to the drive number, which is normally fixed to 0 on a single-disk drive, but can be 0 or 1 on a dual-disk drive (like the 8250LP). In BASIC V4, you can tell the drive to show the directory of the disk in unit 1 on device #8 like thus: CATALOG D8 ON U1, or even copy the contents of a disk in unit 0 to another disk in unit 1 (on the same drive!) with BACKUP U0 TO U1.pallas wrote:On a side note, do you think the "unit" command should be renamed to "dev"? I used the "unit" term because it's used by cc65, which covers many non-cbm systems as well so it must be generic, but I understand the most used cbm term for it is "device", shortcut to "dev".
However, as the number of dual-disk drives is supposedly rather small, it's more an academic problem. They'd all have to be connected to the VIC-20 over IEEE anyway, and then there would be yet another KERNAL expansion on a cartridge in play - where cc65 again would be required to play nice with.
Nethertheless, programs might use the drive number/unit explicitly in the command channel, for example in OPEN 15,8,15, "S0:EXAMPLE.PRG" : CLOSE15, where the drive number is optional between the command (here, Scratch) and the colon. That had been another thing that cropped up during the beta-test phase of the FE3 RAM Disk.