ISO images created by most mastering programs can be mounted as a drive
under DOS using SHSUCDHD.  This format was adopted in the SHSUCD13
release and has not been subsequently changed.  If you did not use a prior
version you need not read the remainder of this document.

                             SHSUCD13
                             May 1996

   Warning! Warning! Warning! Warning! Warning! Warning! Warning! Warning!

The format of the cache images used by the programs in SHSUCD13 differs from
and is not compatable with the cache images of previous versions of SHSUCD.
If you do not use cached images this will not affect you because the change
has no effect on "real drives".

Previous versions did not cache the system area of a CD.  Block zero was
omitted entirely and blocks 1 thru 15 were zeroed.  Programs in this version
cache and use the entire volume space including the system area.  Thus
existing cache images must be converted to the new format before they can
be used by the programs in this archive.

If you do not want to convert existing images you can still use the updated
version of SHSUCDX included in this archive.  The programs SHSUSERV, SHSUCDHD
and CDCACHER all use the new format and cannot be used with old image files.

The conversion consists of appending a 2048 byte block of nulls to the
beginning of the existing cache image.  This can be done with the DOS copy
command and the included 2KBLOCK.DAT file.  The command is:

COPY /b 2KBLOCK.DAT + OLD.IMG NEW.IMG

You must have enough disk space to accomodate both the new image and the old
image while it is being copied.  The old image can be deleted after the
conversion is completed and verified.  Unfortunately, it takes a while to
copy a 650 MByte image.

The new format is compatable with the format of the files created by the
shareware program CD2FILE.  Thus files created with CD2FILE, and perhaps
others that I do not know about, can now be used with both the SHSUCDHD
pseudo driver and the SHSUSERV programs.

My apologies for the problems I am caausing by changing the format.  I
should have changed it long ago.  A request by Olaf Marx
<omarx@adler.biologie.Uni-Osnabrueck.DE> to make it compatable with the
CD2FILE format finally prompted me to get on with it.  Thanks Olaf.