Commodore 1551


Commodore 1551
View of a European Commodore 1551 disk drive, showing the unusual connector

The Commodore 1551 (originally introduced as the SFS 481) was a floppy disk drive for the Commodore Plus/4 home computer. It resembled a charcoal-colored Commodore 1541 and plugged into the cartridge port, providing faster access than the C64/1541 combination. Commodore reportedly planned an interface to allow use of the 1551 with the C64, but it was never released.

Aside from faster access, the drive was very similar to the 1541. Like the 1541, it was a single-sided 170 kilobyte drive for 5¼" disks, with each disk split into 664 256-byte 'blocks' available for user data plus 19 blocks for DOS data and directory; the file system made each block its own cluster. As with the other Commodore single-sided diskette drives 1540 and 1541, both sides of double-sided media could be used only after punching a second write-protection marker hole in the diskette's envelope and inserting the medium upside down into the drive. This became common practice, even more so since single-sided media became rarely available with prices matching those of double-sided disks.

The disk drive used Group Code Recording and contained a MOS Technology 6510T processor as a disk controller. The 6510T was a specialized version of the 6510 processor used in the C64, and it was only used in the 1551. The DOS limited the number of files per disk to 144 regardless of the number of free blocks on the disk because the directory was of a fixed size, and the file system did not allow for subdirectories. The 1551's DOS was compatible with the 1541, so disks written by one drive could be utilized in the other.

The 1551 is less common than other Commodore disk drives. The 1541 was more readily available as it was compatible with the popular C64 and VIC-20, so many people opted to use 1541s with the Plus/4. Since the 1551 was compatible only with the Plus/4, which was a poor seller in the United States, few were made. In Europe, the Plus/4 was much more successful, but because tape drives were the most popular storage device in Europe in the 1980s, the 1551 was not very popular in Europe either.


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Commodore Plus/4 — Plus 4 redirects here. For the trousers, see Plus fours. Commodore Plus/4 Release date 1984 Discontinued 1985 …   Wikipedia

  • Commodore Plus/4 — El Commodore Plus/4 fue un ordenador personal realizado por Commodore International en 1984. El nombre Plus/4 hace referencia al paquete de oficina residente en la memoria ROM compuesta por 4 aplicaciones (procesador de textos, hoja de cálculo,… …   Wikipedia Español

  • Commodore 64 peripherals — Commodore 64 Home Computer This article is about the various external peripherals of the Commodore 64 home computer. Contents 1 Storage …   Wikipedia

  • Commodore DOS — Commodore DOS, aka CBM DOS, was the disk operating system used with Commodore s 8 bit computers. Unlike most other DOS systems before or since which are booted from disk into the main computer s own RAM at startup, and executed there CBM DOS was… …   Wikipedia

  • Commodore 8050 — floppy disk drive, with CBM 2001 PC The Commodore 8050 and Commodore 8250 were dual unit 5¼ floppy disk drives for Commodore International computers. They used a wide rectangular steel case form similar to that of the Commodore 4040, and used the …   Wikipedia

  • Commodore 1581 — The Commodore 1581 is a 3½ inch double sided double density floppy disk drive made by Commodore Business Machines (CBM) primarily for its C64 and C128 home/personal computers. The drive stores 800 kilobytes using an MFM enco …   Wikipedia

  • Commodore 1570 — The Commodore 1570 was a 5¼ floppy disk drive for the Commodore 128 home/personal computer. It was a single sided, 170KB version of the double sided Commodore 1571, released as a stopgap measure when Commodore International was unable to provide… …   Wikipedia

  • Commodore 4040 — The Commodore 4040 and its sibling(s), the 2040 and the European marketed 3040, were dual unit 5¼ floppy disk drives for Commodore International computers. They used a wide case form, and used the IEEE 488 interface common to Commodore PET/CBM… …   Wikipedia

  • Commodore 16 — Der Commodore 16 Der C16 war ein Acht Bit Heimcomputer von Commodore. Er war ein Modell der Commodore 264 Serie und sollte den VC 20 als Einstiegscomputer ersetzen. Inhaltsverzeichnis …   Deutsch Wikipedia

  • Commodore 1541 — Front view of the most common version of the Commodore 1541 disk drive, with open disk slot. This version uses a Newtronics drive mechanism, and the rotating lever is used to hold the disk in place …   Wikipedia