RAMDOS manual


Sidedness and stepping are recorded at &BE3A and &BE3D for drive A & B respectively. They are set to the default values of 0 and &8F on initialisation and can be changed by poking new values. The byte value is worked out as follows (where "x" is any bit value):

  • &Fx = 40 tracks single stepping
  • &8x = 80 tracks single stepping
  • &4x = 40 tracks double stepping
  • &xF = Double sided Flip sided
  • &x8 = Double sided Up and Over A
  • &x4 = Double sided Up and Over B
  • &x2 = Single sided.

One powerful facility of RAMDOS is the ability to read or format tracks whose logical track numbers are different from their physical track numbers. This allows the creation of protected discs which can only be read with RAMDOS. The physical track number is position of the track on the disc (0-39 or 0-79), and the logical track number is the number encoded into the sectors when formatting. The offset is the difference between them. This offset must be poked into &BE39 for drive A and &BE3? [here the original documentation is unclear - DC] for drive B. The default value is zero, which allows the reading of all normal formats.

The formats D10,D20,D40 and D80 hold more data because they use 10 sectors per track, instead of the normal 9.

It should be noted that a disc in drive A with the Buffer format has 200K, but if the whole of this space is to be used, the ALVA should be moved, because it will be too large and will overwrite the DPBB if the Buffer disc is CATed, LOADed to or SAVED from. A new ALVA at (for example) &BE80 could be set by poking this address into &A91E/F.

The number of directory entries is not always the same as the number of files which can be saved when large files are used, because every 16K requires an extra directory space.

The maximum number of files which can be CATed is 140, although any number of files can be DIRed. This is because the buffer for CATing is only 2K long and although this could be enlarged it could cause compatibility problems with other software. Therefore it is best to allocate different types of files to different User groups when a large number of files are kept on a disc. This should also make the disc more organised and easier to use.