Commodore Disk Drives
Commodore's disk drives are unusual in that each contains its own processor and disk operating system, so the drive does the work of managing files rather than the computer.
The PET and CBM business machines used drives on the parallel IEEE-488 bus. The dual 5.25-inch 2040 (sold in Europe as the 3040) was followed by the 4040, holding about 170 KB per disk. The 8050 of 1980, which cost US$1,695, stored about half a megabyte on a single side, and the double-sided 8250 and the single-drive SFD-1001 doubled that to about one megabyte. There were also large 8-inch drives in the 8060 range.
For the home computers, Commodore switched to the cheaper serial bus. The VIC-1540 was designed for the VIC-20, but its timing did not suit the Commodore 64, which led to the famous 1541 of 1982: 170 KB on a single side, priced around US$400, and notoriously slow, which inspired many fast-loaders and replacement operating systems. It was restyled as the beige 1541C in 1986 and as the smaller 1541-II with an external power supply in 1988. The C16 and Plus/4 had the 1551, which connected through the cartridge port and ran about three times faster. The C128 brought the single-sided 1570 and the double-sided 1571, both able to read the MFM format used by CP/M, and in 1987 the 1581 introduced 3.5-inch disks holding about 800 KB, at US$399.
The Amiga used 3.5-inch disks storing 880 KB. Its external drives were the A1010 of 1985, which had a connector for chaining another drive, the redesigned A1011 of 1989, and the CD-1411 of 1991 for the CDTV, identical to the 1011 apart from its colour.
Collectors look for drives that load reliably, noting that 1541 mechanisms came from several suppliers and that later ones are generally more dependable.