2.8 KiB
Disk: Commodore 64
Commodore 64 disks come in two varieties: GCR, which are the overwhelming majority; and MFM, only used on the 1571 and 1581. The latter were (as far as I can tell) standard IBM PC format disks with a slightly odd sector count.
The GCR disks are much more interesting. They could store 170kB on a single-sided disk (although later drives were double-sided), using a proprietary encoding and record scheme; like Apple Macintosh disks they stored varying numbers of sectors per track to make the most of the physical disk area, although unlike them they did it by changing the bitrate rather than adjusting the motor speed.
The drives were also intelligent and ran DOS on a CPU inside them. The computer itself knew nothing about file systems. You could even upload programs onto the drive and run them there, allowing all sorts of custom disk formats, although this was mostly used to compensate for the cripplingly slow connection to the computer of 300 bytes per second (!). (The drive itself could transfer data reasonably quickly.)
A standard 1541 disk has 35 tracks of 17 to 21 sectors, each 256 bytes long (sometimes 40 tracks).
A standard 1581 disk has 80 tracks and two sides, each with 10 sectors, 512 bytes long.
Reading 1541 disks
Just do:
fluxengine read commodore -o commodore.d64
You should end up with an commodore.d64 file which is 174848 bytes long.
You can load this straight into a Commodore 64 emulator such as
VICE.
If you have a 40-track disk, add --196.
Big warning! Commodore 64 disk images are complicated due to the way the tracks are different sizes and the odd sector size, so you need the special D64 or LDBS output formats to represent them sensibly.
Writing 1541 disks
Just do:
fluxengine write commodore -i file.d64
If you have a 40-track disk, add --196.
Note that only standard Commodore 64 BAM file systems can be written this way, as the disk ID in the BAM has to be copied to every sector on the disk.
Reading and writing 1581 disks
1581 disks are just another version of the standard IBM scheme.
Just do:
fluxengine read commodore1581 -o commodore1581.d81
or:
fluxengine write commodore1581 -i commodore1581.img
Reading and writing CMD FD2000 disks
Yet again, these are another IBM scheme variant.
Just do:
fluxengine read cmd_fd2000 -o cmd_fd2000.d81
or:
fluxengine write cmd_fd2000 -i cmd_fd2000.img
Useful references
- Ruud's Commodore Site: 1541: documentation on the 1541 disk format.