With the release of the low priced VIC-20, Commodore rushed to follow
it up with an equally inexpensive disk drive. The Commodore 1540
was the result. Strangely enough, the 1540 must have been too expensive
even still, as they are very rare in their original VIC-20 formulation.
The 1540 was the first disk drive on the new Commodore serial bus. Unfortunately, due to a timing error in the new I/O chips, the engineers were forced to slow down the throughput of this drive considerably. When the Commodore 64 was designed, instead of fixing this problem, Commodore decided to keep the C64 compatible with this disk drive by slowing it down as well. Ironically, the C64 serial bus had to be slowed even further due to a conflict with the new VIC-II video chip, making the C64 incompatible with the 1540 anyway (unless one disabled the VIC-II video chip temporarily using software).
The German counterpart to the VIC-1540 was the VC-1540. You might want to check out the VC-20 page for some speculation on the name difference.
Although these disk drives used a new serial interface, the principle design of Commodore disk drives and CBM DOS remained the same. Like all Commodore disk drives, these drives were "smart" devices. They included their own processor, their own memory, and their own disk operating system. In fact, the relationship between a Commodore computer and it's disk drive resembles more closely two computers on a network than a typical Computer->peripheral relationship. The peripherals on the Commodore serial "network" each had a unique identifying "Unit" number, typically ranging from 8-30. This number identified which physical device was being accessed. When a disk drive contained more than one floppy drive (like the 1572 for instance), you also had to refer to the particular "drive" number you wanted (typically 0 or 1). Single-floppy drives, like the ones on this page, still had to deal with the legacy of the old IEEE-488 dual drives and the version of CBM DOS with which they were compatible by referring to their single floppy as "drive 0".
Model : VIC-1540 Type : 5.25" Floppy Disk Media : Single Sided, Single Density Capacity : 170K per disk Interface: CBM Serial Bus Dos : CBM DOS 2.6 Notes :
Model : VC-1540 Type : 5.25" Floppy Disk Media : Single Sided, Single Density Capacity : 170K per disk Interface: CBM Serial Bus Dos : CBM DOS 2.6 Notes :
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