Games - Commodore 1541

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	Games - Commodore 1541

The Commodore 1541 (aka CBM 1541, and originally called VIC-1541), made by Commodore International, was the best-known floppy disk drive for the Commodore 64 home computer. The 1541 was a single-sided 170 kilobyte drive for 5¼" disks. The 1541 followed the previous Commodore 1540 (meant for the VIC-20).

The disk drive used Group Code Recording (GCR) and contained a MOS 6502 microprocessor, doubling as a disk controller and on-board disk operating system processor. The number of sectors per track varied from 17 to 21 (an early implementation of Zone Bit Recording). The drive's built-in disk operating system was CBM DOS 2.6.

Use of "flippy disks" ("made" by cutting/punching a notch on the left-hand side of a double-sided disk, opposite the factory-made write-protect hole) would give access to the 'reverse' side of the disks, doubling the storage capacity. Each side of 170 KB was split into 664 'blocks' holding 256 bytes each; the file system made each block its own cluster.

Introduction and early problems

Priced at under US$400 at its introduction, the 1541 became widely popular. Although expensive by today's standards, a C64 plus a 1541 cost about $900, while an Apple II with no disk drive cost $1395. The demand caught Commodore by surprise, who struggled to produce the drive in adequate quantities.

Failure rates on the 1541 initially were very high, and the drives were virtually impossible to find. The lead editorial in the December 1983 issue of Compute!'s Gazette lamented that four of the seven drives the magazine had in its editorial offices had failed. Eventually the problems subsided and the drive became nearly as widely available as the C64 itself.

Versions and third-party clones

There were two versions of the 1541 mechanics. Early models used a drive mechanism made by Alps Electric, distinguishable by its push-down drive door. Later models utilized a drive mechanism manufactured by Newtronics (Mitsumi), which used a lever release. All but the very earliest 1541s can use either the Alps or Newtronics mechanism. Visually, the first models, of the VIC-1541 denomination, had an off-white color like the VIC-20 and VIC-1540. Then, to match the look of the C64, CBM changed the drive's color to brown-beige and the name to Commodore 1541.

The 1541's numerous shortcomings opened a market for a number of third-party clones of the disk drive, a situation that continued for the lifetime of the C64. Well-known clones were the Oceanic OC-118 aka Excelerator+, MSD 's single and dual drives, the Enhancer 2000, the Indus GT, and CMD
's FD-2000 and FD-4000. Nevertheless, the 1541 became the first disk drive to see widespread use in the home and Commodore sold millions of the units.

In 1986, Commodore released the 1541C, a revised version that offered quieter and slightly more reliable operation and a light beige case matching the color scheme of the Commodore 64C. It was replaced in 1988 by the 1541-II, which used an external power supply to provide cooler operation and allow the drive to have a smaller desktop footprint (the power supply "brick" being placed elsewhere, typically on the floor).

The serial computer interface

The 1541 used a bit-serial version of the IEEE-488 interface, the speedier parallel version of which was used on Commodore's earlier drives for the PET/CBM range of personal/business computers. To ensure a ready supply of inexpensive cabling for its home computer peripherals, Commodore chose standard DIN connectors for the serial interface. Disk drives and other peripherals such as printers were connected to the computer via a daisy-chain scheme, necessitating only a single connector on the computer itself.

[ Visit the complete Wikipedia entry for Commodore 1541 ]

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commodore 1541

Games - Commodore 1541

Introduction and early problems

Versions and third-party clones

The serial computer interface

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