Compucolor II disk

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File Format
Name Compucolor II disk
Released 1978

The Compucolor II computer came standard with a 5.25" disk drive, built into its TV-based monitor. (The earlier Compucolor I had used an 8-Track tape for data storage.)

The disk format was single-sided (but disks could be flipped), with 40 tracks and 48tpi density. It had an average access time of 400 ms and latency of 200 ms, with transfer rate 76.8 kilobits/sec. Formatted capacity was 51.2 kilobytes per side.

The Compucolor filesystem was implemented the same way in the disk-based systems as the earlier tape-based ones, so it treated the disk as if it were a tape, moving all subsequent files backward to fill the space when a file was deleted.

According to the podcast linked below, the CompuColor disk drive based its writing speed on the exact details of the electric current coming into it, which could vary between different CompuColor machines and even in the same one over time, making it an iffy proposition to read disks from somebody else or from a long time earlier.


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