Would it be possible to add support for 86box (PCem fork) native .86F format? I've already contacted Jean-Francois by email but I thought I should post it here just in case. The emulator is not as popular as PCem or DOSBox yet, but it is VERY promising. Take a look at .86F specifications, please:
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00000000: Magic 4 bytes ("86BF")
00000004: Minor version (0E)
00000005: Major version (02)
00000006: Disk flags (16-bit)
Bit 0 Has surface description data (1 = yes, 0 = no)
This data indicates if the corresponding bit on the FM/MFM encoded surface
is a normal bit or a special bit (weak bit or hole, depending on the other bit):
0 = The corresponding FM/MFM encoded surface bit is normal
1 = The corresponding FM/MFM encoded surface bit is either a weak bit or a hole:
Corresponding FM/MFM encoded bit is 0: Hole (noise on read, not overwritable)
Corresponding FM/MFM encoded bit is 1: Weak bit (noise on read, overwritable)
Bits 2, 1 Hole (3 = ED + 2000 kbps, 2 = ED, 1 = HD, 0 = DD)
Bit 3 Sides (1 = 2 sides, 0 = 1 side)
Bit 4 Write protect (1 = yes, 0 = no)
Bits 6, 5 RPM slowdown (3 = 2%, 2 = 1.5%, 1 = 1%, 0 = 0%)
Bit 7 Bitcell mode (1 = Extra bitcells count specified after
disk flags, 0 = No extra bitcells)
The maximum number of extra bitcells is 1024 (which
after decoding translates to 64 bytes)
Bit 8 Disk type (1 = Zoned, 0 = Fixed RPM)
Bits 10, 9 Zone type (3 = Commodore 64 zoned, 2 = Apple zoned,
1 = Pre-Apple zoned #2, 0 = Pre-Apple zoned #1)
Bit 11 Data and surface bits are stored in reverse byte endianness
Bit 12 If bits 6, 5 are not 0, they specify % of speedup instead
of slowdown;
If bits 6, 5 are 0, and bit 7 is 1, the extra bitcell count
specifies the entire bitcell count
Bit 13 Revolutions (0 = one revolution, 1 track has 16-bit number of revolutions)
00000008: Offsets of tracks
Note that thick-track (eg. 360k) disks will have (tracks * 2) tracks, with each pair of tracks
being identical to each other.
Each side of each track is stored as its own track, in order (so, track 0 side 0, track 0 side 1,
track 1 side 0, track 1 side 0, etc.).
Track offset + 00000000: Track flags (16-bit)
Bits 7, 6, 5 RPM
000 = 300 rpm
001 = 360 rpm
Bits 4, 3 Encoding
00 = FM
01 = MFM
10 = M2FM
11 = GCR
Bits 2, 1, 0 Bit rate, if encoding is MFM:
000 = 500 kbps
001 = 300 kbps
010 = 250 kbps
011 = 1000 kbps
101 = 2000 kbps
If encoding is FM, the bit rate is half that.
If extra bitcell count is present:
Track offset + 00000002: Extra (or total, depending on disk flags) bit cells count (32-bit)
If this specifies extra bit cells rather than total, it is a signed
integer, and when negative, makes the track smaller.
Track offset + 00000006: Bit cell where index hole is (32-bit)
Track offset + 0000000A: FM/MFM/M2FM/GCR-encoded data (track length bytes)
Track offset + 0000000A + track length: Surface description data if present (track length bytes)
Else:
Track offset + 00000002: Bit cell where index hole is (32-bit)
Track offset + 00000006: FM/MFM/M2FM/GCR-encoded data (track length bytes)
Track offset + 00000006 + track length: Surface description data if present (track length bytes)
If this is a multi-revolution 86F, then track offset + 00000004 has a 16-bit number of track revolutions,
everything after it is moved ahead by 2 bytes, and FM/MFM/M2FM/GCR-encoded data appears (number of
revolutions) times rather than once, while surface decription data, if present, only appears once.
Track lengths:
Hole 0 (DD) or 1 (HD):
2.0% RPM slowdown: 12750 words
1.5% RPM slowdown: 12687 words
1.0% RPM slowdown: 12625 words
0.0% RPM slowdown/speedup: 12500 words
1.0% RPM speedup : 12376 words
1.5% RPM speedup : 12315 words
2.0% RPM speedup : 12254 words
Hole 2 (ED):
2.0% RPM slowdown: 25250 words
1.5% RPM slowdown: 25375 words
1.0% RPM slowdown: 25250 words
0.0% RPM slowdown/speedup: 25000 words
1.0% RPM speedup : 24752 words
1.5% RPM speedup : 24630 words
2.0% RPM speedup : 24509 words
Hole 3 (ED + 2000 kbps):
2.0% RPM slowdown: 51000 words
1.5% RPM slowdown: 50750 words
1.0% RPM slowdown: 50500 words
0.0% RPM slowdown/speedup: 50000 words
1.0% RPM speedup : 49504 words
1.5% RPM speedup : 49261 words
2.0% RPM speedup : 49019 words
1 word = 2 bytes (so 16 bits)
If extra bit cells count is present and it indicates extra bit cells count:
Track length = (Track length << 4) + Extra bitcells count
If (Track length & 15)
Track length + (Track length >> 4) + 1
Else
Track length + (Track length >> 4)
If extra bit cells count is present and it indicates total bit cells count,
then the total bit cells count become the track length.