The header is 64 bytes. The layout is from the VICE manual (chapter 17, section X64), read through a summarising fetch tool, so it is “our words”.
Fields
| Offset | Size | Meaning |
|---|---|---|
$00 | 4 | Magic: 43 15 41 64 |
$04 | 1 | Header version, major: 1 |
$05 | 1 | Header version, minor: 1, with 2 in use too |
$06 | 1 | Device type (below) |
$07 | 1 | The highest track: 35 for the 1540, 1541, 1570 and 1571, 80 for the 1581 |
$08 | 1 | Sides: 0 for one side, 1 for a second side; the manual says it must be 0 for the 1541 and 1581 |
$09 | 1 | Error data flag |
$0A–$1F | 22 | Unused |
$20–$3E | 31 | Image description, ASCII or Latin-1 |
$3F | 1 | Always $00 |
$40 | – | The disk image begins |
The viewer does not use the highest track, sides and error flag: it reads the image from the device type and the size.
Device types
| Code | Drive | Disk image behind the header (this viewer) |
|---|---|---|
$00 | 1540 | D64 |
$01 | 1541 (the default) | D64 |
$02 | 1542 | D64 |
$03 | 1551 | no layout |
$04 | 1570 | D71 |
$05 | 1571 | D71 |
$06 | 1572 | no layout |
$08 | 1581 | D81 |
$10 | 2031 or 4031 | no layout |
$11 | 2040 or 3040 | no layout |
$12 | 2041 | no layout |
$18 | 4040 | no layout |
$20 | 8050 | D80 |
$21 | 8060 | no layout |
$22 | 8061 | no layout |
$30 | SFD-1001 | no layout |
$31 | 8250 | D82 |
$32 | 8280 | no layout |
The mapping of a device to a plain image format is ours: the manual’s summary says the image is “a standard image (D64, D71 and so on)” and names the maximum tracks for the 1540/1541/1570/1571 and the 1581 only. For the 1570 and 1571 that the disk is a D71, and for the 8050 and 8250 that it is a D80 and a D82, is our inference.
Not described
Known, not yet covered
- The layouts of the disks of the “no layout” devices.
Unknown
- The meaning of the sides byte and the error data flag beyond the one line above.