Date   : Mon, 09 Feb 2004 16:58:27 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: [Fwd: Re: BBC floppy / drive formats]

I asked a similar Q a while back in terms of disk formats only - the
following is Jonathan's (trimmed) response:

xxxxxxxxxxx
 
See http://www.mdfs.net/Docs/Comp/Disk/Densities and
http://www.mdfs.net/Docs/Comp/Disk/Format/Formats
 
In summary:
 
                           Disk Formats
                           ------------
Media Mod. Sides  Tracks  Sectors  Numbers BytesPerSector  Media Size
  DD   FM    1      40      10       0-9        256           100k
  DD   FM    2      40      10       0-9        256           200k
  DD   FM    1      80      10       0-9        256           200k
  DD   FM    2      80      10       0-9        256           400k
  DD  MFM    1      40       9       0-8        512           180k
  DD  MFM    1      40       9       1-9        512           180k
  DD  MFM    2      40       9       0-8        512           360k
  DD  MFM    2      40       9       1-9        512           360k
  DD  MFM    1      80       9       0-8        512           360k
  DD  MFM    1      80       9       1-9        512           360k
  DD  MFM    2      80       9       0-8        512           720k
  DD  MFM    2      80       9       1-9        512           720k
  DD  MFM    1      40      16       0-15       256           160k
  DD  MFM    2      40      16       0-15       256           320k
  DD  MFM    1      80      16       0-15       256           320k
  DD  MFM    2      80      16       0-15       256           640k
  DD  MFM    2      80       5       0-4       1024           800k
  HD  MFM    2      80      10       0-9       1024          1600k
  HD  MFM    2      80      18       1-18       512          1440k
  HD  MFM    2      80      15       1-15       512          1200k
 
Once a disk has been formatted, you can put any filesystem in it. There
are usual combinations, eg 1*80*10*256 usually has DFS in it and
1*80*16*256 usually has ADFS in it, but it's just as easy to put DFS in
1*80*16*256, which is one of the options Watford's DDFS gives you.
 
Filesystem Formats
DFS:
Directory Size=&0200
Free Space Map=implied
Root          =&0000-&0001
Deblocked     =No
 
Watford DFS:
Directory Size=&0400
Free Space Map=implied
Root          =&0000-&0003
Deblocked     =No
 
ADFS S,M,L:
Directory Size=&0500
Free Space Map=&0000,&0001
Root          =&0002-&0006
Deblocked     =No
 
ADFS D,E,F:
Directory Size
Free Space Map=  ... check RISC OS PRMs
Root         
Deblocked     =No
 
Acorn CPM:
Directory Size=&1000
Free Space Map=implied  
Root          =&001E00
Deblocked     =Yes
 
HADFS:
Directory Size=&0300
Free Space Map=&0046
Root          =&0047
Deblocked     =No
 
Most Acorn formats use H:C:S numbering, ie:
 logical sector=Side*TracksPerSide+Track*SecPerTrack+Sector
 
32bit ADFSs also use C:H:S numbering, ie:
 logical sector=Track*SecPerTrack*Sides+Side*SecPerTrack+Sector
 
There are many others. I'm updated some documents on my website about
details of filesystem structures.