Commodore Floppy Disk Drives
The VIC-1541 (or just 1541)
This was the most popular floppy disk drive, commonly seen attached to Commodore 64 computers. It was a single-sided 170K drive for 5.25" floppy diskettes. It was the successor to the 1540 floppy drive suitable for the VIC-20 computer.
At a technical level, the drive used GCR (Group Code Recording) and contained a MOS 6502 microprocessor, just the same as found in the C64 itself! The 6502 doubled up as a disk controller and disk operating system (DOS) processor. There were two different drive mechanisms found in the 1541: early models used the Alps Electric mechanism, recognisable by the "pull down" drive door. Later models used the Newtronics (Mitsumi) mechanism which used the more modern level release to the side of the disk. The first models were an off-white colour to match the VIC-20's colour, and were called "VIC-1541". Then to match the C64, Commodore coloured their 1541 the beige colour of the C64 and the name of the drive changed to Commodore 1541 (see image above). Initially, Commodore intended to use a hardware shift register (the 6522 VIA) to maintain relatively brisk drive speeds with the new serial interface. However, a hardware bug with this chip prevented the initial design from working as anticipated, and the ROM code was hastily rewritten to handle the entire operation in software. According to Jim Butterfield, this caused a speed reduction by a factor of five.
When the Commodore 64C was released in 1986, they gave the same facelift to the 1541, and rebranded it 1541C. This took the livery of the 64C, with a light beige case colour. It was more reliable and had a quieter operation than its predecessors, although no quicker in operation.
Then in 1988, the power supply was taken of the case in order to provide a cooler operation, and this went into a "brick". The drive unit itself could then take a much sleeker form factor. This model they branded the 1541-II.
As implemented on the VIC-20 and Commodore 64, CBM DOS could transfer only about 300 bytes per second, which translated to about 20 minutes to copy one disk—10 minutes of reading time, and 10 minutes of writing time. However, since both the computer and the drive could easily be reprogrammed, third parties quickly wrote more efficient firmware that would speed up drive operations drastically. Without hardware modifications, some "fast loader" utilities managed to achieve speeds of up to 4 kB/s. The most common of these products were the Epyx FastLoad, the Final Cartridge, and the Action Replay plug-in cartridges, which all had machine code monitor and disk editor software on board as well.