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 Post subject: Re: Some questions
PostPosted: December 22nd, 2014, 5:56 am 
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This is also a valid X6800 .xdf format:

78/2/8x 1024 Sharp X68000 78-Track 1277952 bytes


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 Post subject: Re: Some questions
PostPosted: February 10th, 2015, 7:02 am 
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etabeta wrote:
I have sort of reverse engineered the .FDD format for supporting it in MESS
The file structure seems relatively easy

...

the main thing to account when converting / handling these is the fact that any sector with constant value is skipped in the disk (to save space, I guess) and it has to be manually padded


Thanks for this - a great help.

The sector map seems to provide for up to 160 tracks of up to 26 sectors each. This leaves, in the header, 32 bytes at the end - samples I have either have these filled with H"00", or data of some kind.


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 Post subject: Re: Some questions
PostPosted: February 13th, 2015, 9:42 am 
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etabeta wrote:
I have sort of reverse engineered the .FDD format for supporting it in MESS
The file structure seems relatively easy

Code:
0xC3FC header, followed by raw sector data
    Sector map starts at offset 0xDC, with 12bytes for each sector

    Each entry of the sector map has the following structure
    - 0x0 = track number (if 0xff the sector/track is unformatted/unused)
    - 0x1 = head number
    - 0x2 = sector number
    - 0x3 = sector size (128 << this byte)
    - 0x4 = fill byte. if it's not 0xff, then this sector in the original
            disk consisted of this single value repeated for the whole
            sector size, and the sector is skipped in the .fdd file.
            if it's 0xff, then this sector is wholly contained in the .fdd
            file
    - 0x5 = ??
    - 0x6 = ??
    - 0x7 = ??
    - 0x8-0x0b = absolute offset of the data for this sector, or 0xfffffff
                 if the sector was skipped in the .fdd (and it has to be
                 filled with the value at 0x4)


the main thing to account when converting / handling these is the fact that any sector with constant value is skipped in the disk (to save space, I guess) and it has to be manually padded


If the fill byte is H"FF" and the absolute offset is H"FFFFFFFF", then the sector needs to be padded with H"FF". That one caught me for a while. I hope I have it right now. ;)


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 Post subject: Re: Some questions
PostPosted: March 28th, 2015, 9:14 am 
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peter_j wrote:
If the fill byte is H"FF" and the absolute offset is H"FFFFFFFF", then the sector needs to be padded with H"FF". That one caught me for a while. I hope I have it right now. ;)


that was the way I implemented the disk handling in MESS because it was the easiest way to proceed (check first the offset map and, whenever offset is 0xFFFFFFFF, use the corresponding fill byte value), but I had never noticed a disk with 0xff padding.
good to have it confirmed, though


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 Post subject: Re: Some questions
PostPosted: April 6th, 2015, 3:51 am 
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I am just posting this here for reference, from

http://datacrystal.romhacking.net/wiki/X68k:FD_Format

Image

See also:

http://gamesx.com/wiki/doku.php?id=x680 ... _on_x68000


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 Post subject: Re: Some questions
PostPosted: June 1st, 2015, 4:01 pm 
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http://mijet.eludevisibility.org/X68000 ... MAT_en.txt

Code:
*1: Bytes/Sector
*2: Sectors/Track
*3: Number of Cylinders
*4: FAT Sectors x Copies
*5: Root Directory Sectors
*6: Reserved Sectors
*7: Total Sectors
*8: Total Volume (in KB)
*9: Free Area (in KB)

 ------------------------------------------------------------------
|Type|FAT ID| MB | PDA| *1 | *2 | *3 | *4 | *5 | *6 | *7 | *8 | *9 |
|------------------------------------------------------------------|
| 2HD  | FE | FE | 90 |1024|  8 | 77 | 2×2|  6 |  1 |1232|1232|1221|
| 2HDA | FE | ** | ** |1024|  8 | 80 | 2×2|  6 |  1 |1280|1280|1269|
| 2HDE | F8 | EC | ** |1024|  9 | 80 | 3×2|  6 |  1 |1440|1440|1427|
| 2HC  | F9 | FD | 90 | 512| 15 | 80 | 7×2| 14 |  1 |2400|1200|1185|
| 2HCE | F8 | ** | ** | 512| 18 | 80 | 9×2| 14 |  1 |2880|1440|1423|
| 2HQ  | F0 | FA | 70 | 512| 18 | 80 | 9×2| 14 |  1 |2880|1440|1423|
| 2HQ16| ?? | ?? | ?? | 512| 20 | 80 |10×2| 14 |  1 |3200|1600|1582|
| 2HS  | FB | EB | ** |1024|  9 | 80 | 3×1|  6 |  1 |1440|1440|1430|
| 2HT  | FA | EA | ** |----|----| 80 | 3×1|  5 |  1 |----|1599|1590|
| 2DD  | FB | FB | 10 | 512|  8 | 80 | 2×2|  7 |  1 |1280| 640| 634|
| 2DD  | F9 | FC | 30 | 512|  9 | 80 | 3×2|  7 |  1 |1440| 720| 713|
| 2DD  | E0 | E0 | ** | 512| 10 | 80 | 3×2|  7 |  1 |1600| 800| 793|
| 2D   | FF | E8 | ** | 512|  8 | 40 | 1×2|  7 |  1 | 640| 320| 315|
| 2D   | FD | E6 | ** | 512|  9 | 40 | 2×2|  7 |  1 | 720| 360| 354|
| 2ED  | F0 | ** | ** | 512| 36 | 80 | 9×2| 15 |  1 |5760|2880|2863|
|------------------------------------------------------------------|
| 1DD  | FA | EF | ** | 512|  8 | 80 | 1×2|  7 |  1 | 640| 320| 315|
| 1DD  | F8 | EE | ** | 512|  9 | 80 | 2×2|  7 |  1 | 720| 360| 354|
| 1D   | FE | E7 | ** | 512|  8 | 40 | 1×2|  4 |  1 | 320| 160| 156|
| 1D   | FC | E5 | ** | 512|  9 | 40 | 2×2|  4 |  1 | 360| 180| 175|
 ------------------------------------------------------------------

Editor's Notes:

Tracks = Cylinders * Heads

I believe the number of cylinders can actually go up to at least 82
in some cases.


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