DCU/DCP File Format

File format documentation

This is not a dedicated emulator format, but instead, a disk image created by the DOS utility Disk Image Pro (Sometimes called "Disk Copy Pro", hence the DCP)

The format itself is quite simple, but the list of media bytes may not be accurate, at least as observed in the wild.

The details below are taken from posts on the FMV forums, except for remarks in Italics which are my notes.

DCP/DCU Header
0000h: BYTE Media Type 
0001h ~ 00A1h: BYTE Track map
00A2h: BYTE All cylinders stored flag
00A3h ~: Disk image

DCP/DCU Media Type Flags

01h: 2HD-8 sector (1.25MB) (BKDSK .HDM) (aka 2HS)
2 heads, 77 cylinders, 8 sectors/track, 1024 bytes/sector = 1,261,568 bytes (360rpm)

02H: 2HD-15 sector (1.21MB) (BKDSK .HD5) (aka 2HC)
2 heads, 80 cylinders, 15 sectors/track, 512 bytes/sector = 1,228,800 bytes (360rpm)

03H: 2HQ-18 sector (1.44MB) (BKDSK .HD4) (aka 2HDE)
2 heads, 80 cylinders, 18 sectors/track, 512 bytes/sector = 1,474,560 bytes (300rpm)

04H: 2DD-8 sector (640KB) (BKDSK .DD6)
2 heads, 80 cylinders, 8 sectors/track, 512 bytes/sector = 655,360 bytes (300rpm)

05h: 2DD-9 sector ( 720KB) (BKDSK .DD9)
2 heads, 80 cylinders, 9 sectors/track, 512 bytes/sector = 737,280 bytes (300rpm)

08h: 2HD-9 sector (1.44MB)
2 heads, 80 cylinders, 9 sectors/track, 1024 bytes/sector = 1,474,560 bytes (300rpm)(??)

First Track: 26 sectors/track, 128 bytes/sector
Rest of cylinders: 2 heads, 77 cylinders, 26 sectors/track, 256 bytes/sector 
153*26*256 + 26*128 = 1,021,696 bytes of data in disk image

2 heads, 80 cylinders, 16 sectors/track, 256 bytes/sector = 655,360 bytes (300rpm)

21H: 2HD-26 sector
2 heads, 80 cylinders, 26 sectors/track, 256 bytes/sector = 1,064,960 bytes (??rpm)(??)

Other Values

All cylinders Stored Flag: This, in practice seems often to be set strangely or incorrectly. DCP always set to 0. DCU - 1 if all cylinders stored, 0 if not.

Track Map: 160 bytes, each representing a track, 1 if present, 0 if not. Not always accurate in the real world.

Disk Image: Disk data, layout depending on Media Type (In C/H/S order). Gets padded with E5 hex on conversion to FDI by VFIC.

Additional Notes

Overtracked Images
As this image format supports a maximum of 160 cylinders, overtracked images cannot be properly converted to this format.

HexEditor View

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