Commodore 64 Peripherals - Storage - Floppy Disk Drives

Floppy Disk Drives

Although usually not supplied with the machine, floppy disk drives of the 5¼ inch (1541, 1570 and 1571) and, later, 3½ inch (1581) variety were available from Commodore.

The 1541 was the standard floppy disk drive for the Commodore 64, with nearly all disk-based software programs released for the computer being distributed in the 1541 compatible floppy disk format. The 1541 was very slow in loading programs because of a poorly implemented serial bus, a legacy of the Commodore VIC-20.

The 1541 disk drive was notorious for not only its slow performance and large physical size compared to the C64 (the drive is almost as deep as the computer is wide), but also for its mechanical unreliability. Perhaps the most common failure involved the drive's read-write head mechanism. Many complex software copy-protection schemes used data stored on nonstandard tracks on floppies, forcing the drive, while reading the data, to seek to track zero, which caused the head drive mechanism to slam into a mechanical stop. This produced a loud, telltale knocking sound and, more seriously, would over time often move the head mechanism out of precise alignment, resulting in read errors and necessitating repairs. Some demos even exploited this to force the disk drive to play crude tunes ("Bicycle Built For Two" was one) by varying the knocking of the mechanism.

Also, as with the C64, 1541 drives tended to overheat due to a design that did not permit adequate cooling (potentially fixed by mounting a small fan to the case). Many of the 1541's design problems were eventually rectified in Commodore's 1541-II disk drive, which was compatible with the older units. The power supply unit was not housed inside the drive case; hence, the 1541-II size was significantly smaller and did not overheat.

In the following example, '*' designates the last program loaded, or the first program on the disk, '8' is the disk drive device number, and the '1' signifies that the file is to be loaded not to the standard memory address for BASIC programs, but to the address where its program header tells it to go—the address it was saved from. This last '1' usually signifies a machine language program.

Not long after the 1541's introduction, third-party developers demonstrated that performance could be improved with software that took over control of the serial bus signal lines and implemented a better transfer protocol between the computer and disk. In 1984 Epyx released its FastLoad cartridge for the C64, which replaced some of the 1541's slow routines with its own custom code, thus allowing users to load programs in a fraction of the time. Despite being incompatible with many programs' copy protection schemes, the cartridge became so popular among grateful C64 owners (likely the most-widespread third-party enhancement for the C64 of all time) that many Commodore dealers sold the Epyx cartridge as a standard item when selling a new C64 with the 1541.

As a free alternative to FastLoad cartridges, numerous pure software turbo-loader programs were also created that were loaded to RAM each time after the computer was reset. The best of these turbo-loaders were able to accelerate the time required for loading a program from the floppy drive by a factor of 20x, demonstrating the default bus implementation's inadequacy. As turbo-loader programs were relatively small, it was common to place one on almost each floppy disk so that it could be quickly loaded to RAM after restart.

The 1541 floppy drive contained a MOS 6502 processor acting as the drive controller, along with a built-in disk operating system (DOS) in ROM and a small amount of RAM, the latter primarily used for buffer space. Since this arrangement was, in effect, a specialized computer, it was possible to write custom controller routines and load them into the drive's RAM, thus making the drive work independently of the C64 machine. In fact, there were many software packages that took advantage of this; for example, certain back up software allowed users to make multiple disk copies directly between daisy-chained drives without a C64.

Several third party vendors sold an IEEE-488 general purpose interface bus adapter for the C64, which plugged into the machine's expansion port. Outside of BBS operators, few C64 owners took advantage of this arrangement and the accompanying IEEE devices that Commodore sold (such as the SFD-1001 1-megabyte 5¼ inch floppy disk drive, and the peripherals originally made for the IEEE equipped PET computers, such as the 4040 and 8050 drives and the 9060/9090 hard disk drives).

As an alternative to the feeble performing 1541 or the relatively expensive IEEE bus adapter and associated peripherals, a number of third-party serial-bus drives such as the MSD Super Disk and Indus GT appeared that often offered better reliability, higher performance, quieter operation, or simply a lower price than the 1541, although often at the expense of software compatibility due to the difficulty of reverse engineering the DOS built into the 1541's hardware (Commodore's IEEE-based drives faced the same issue due to the dependence of the DOS on features of the Commodore serial bus).

Like the IEEE-488 interface, the serial bus offered the ability to daisy chain hardware together — that is, one device (disk drive or printer) would be connected to the Commodore 64 and the others would be connected to each other in sequence. This led to Commodore producing (via a third party) the Commodore 4015, or VIC-switch. This device (now rarely seen) allowed up to 8 Commodore 64s to be connected to the device along with a string of peripherals, allowing each computer to share the connected hardware.

It was also possible, without requiring a VIC-switch, to connect two Commodore 64s to one 1541 floppy disk drive to simulate an elementary network, allowing the two computers to share data on a single disk (if the two computers made simultaneous requests, the 1541 admirably handled one whilst returning an error to the other, which surprised many people who expected the 1541's less-than-stellar drive controller to crash or hang). This functionality also worked with a mixed combination of PET, VIC-20, and other selected Commodore 8-bit computers.

In the mid-1980s, a 2.8-inch floppy disk drive, the Triton Disk Drive and Controller, was introduced by Radofin Electronics, Ltd. It was compatible with the Commodore 64 as well as other popular home computers of the time, thanks to an operating system stored on an EPROM on an external controller. It offered a capacity of 144/100 kilobytes non-formatted/formatted, and data transfer rates of up to 100 kilobytes per second. Up to 20 files could be kept on each side of the double-sided floppy disks.

Later in the 1990s, Creative Micro Designs produced several powerful floppy disk drives for the Commodore 64. These included the FD-Series serial bus compatible 3.5" floppy drives (FD-2000, FD-4000), which were capable of emulating Commodore's 1581 3.5" drive as well as implementing a native mode partitioning which allowed typical 3.5" high-density floppy disks to hold 1.6 MB of data—more than MS-DOS's 1.4 MB format. The FD-4000 drive had the advantage of being able to read hard-to-find enhanced floppy disks and could be formatted to hold 3.2 MB of data. In addition, the FD series drives could partition floppy disks to emulate the 1541, 1571 and 1581 disk format (although unfortunately, not the emulated drive firmware), and a real time clock module could be mounted inside the drive to time-stamp files. Commercially, very little software was ever released on either 1581 disk format or CMD's native format. However, enthusiasts could use this drive to transfer data between typical PC MS-DOS and the Commodore with special software, such as SOGWAP's Big Blue Reader.

There was one other 3.5" floppy drive available for the Commodore 64. The "TIB 001" was a 3.5" floppy drive that connected to the Commodore 64 via the expansion port, meaning that these drives were very fast. The floppy disks themselves relied on an MS-DOS disk format, and being based on cartridge allowed the Commodore 64 to boot from them automatically at start-up. These devices appeared from a company in the United Kingdom, but unfortunately did not become widespread due to non-existent third-party support. In an article in Zzap!64 of November 1991, several software houses interviewed believed that the device came to the market too late to be worthy of supporting.