MSD Super Disk
The MSD Super Disk was a series of 5¼" floppy disk drives compatible to some degree with C1541 and produced by Micro Systems Development (Dallas, Texas; later MSD Systems) for use with Commodore 8-bit home computers. Two different versions of the MSD Super Disk were available: the single-drive SD-1 and the dual-drive SD-2.
Introduced in 1983, the MSD Super Disk drives were the first third-party devices designed for compatibility with the Commodore 64, although other manufacturers soon followed suit. The MSD drives included both an IEEE-488 parallel interface and the custom Commodore serial interface. Therefore, they could be connected to any Commodore 8-bit system, from the Commodore PET to the C64 and C128, without any converters or add-on devices.
Features and pricing
The MSD SD-1 was more expensive than the Commodore 1541. For instance, a typical mail-order advertisement in the January 1985 issue of RUN Magazine (p. 91) lists the MSD SD-1 single drive at $249.95, compared to $199.95 for the Commodore 1541. The dual drive SD-2 was listed at $449.95, much less than the comparable Commodore PET dual drive CBM 4040 which sold for $699 (Byte magazine, August 1983, p. 311).
However, they did offer several advantages to justify the higher price. In an August 1985 review of 1541 replacements, RUN Magazine wrote that the MSD SD-2 was "built like a tank and can run 24 hours a day for weeks" (p. 28).
Due to the serial interface's limitations, program loading and saving was no faster than on a 1541 drive when that interface was used. However, the SD-1 and SD-2 were several times faster when connected via the IEEE-488 interface. MSD Systems also offered the VIE and CIE IEEE-488 interface for the VIC-20 and Commodore 64, respectively. A blank disk could be formatted in only 18 seconds on the MSD Super Disk series, compared to 1 minute and 22 seconds on the 1541 (p. 26).
The MSD SD-2 implemented the Commodore DOS Duplicate command from the old Commodore PET dual drive series. Because the SD-2 had paired drive units and 6kB of internal RAM, it allowed entire disks to be copied in less than 2-minutes. It was still unable to read and write an entire track of data (over 7kB) in a single rotation of the media which is optimal. It did have an empty PCB pad available to add 4th 2kB chip. A third-party hardware & software add-on (Chip Level Designs' Mass Duplicator) was produced to add the extra RAM and allow for full-track-per-rotation 22-second disk duplication.
The BASIC Copy command could also be used to copy files from one drive to another on the MSD SD-2, a feature not available with two 1541 single drives. However, the MSD Super Disk drives had difficulty loading most copy-protected software, due to substantial differences in the DOS code and memory mapping.
Internally, both models featured TEC brand (model FB-501) floppy drive mechanisms. The electronics on the mechanisms was modified by MSD to be compatible with the GCR recording format used by all Commodore disk drives at the time. The main control board utilized a 1 MHz Rockwell International 6511Q microcontroller.
Ahoy! noted the SD-2's incompatibilities with some 1541 software, but concluded that "serious users of the Commodore 64 will easily be able to justify the $695 price tag. The time savings alone, when backing up disk files, will rapidly pay for the machine", and also a good replacement for the CBM 4040.