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Here is a patch for RAMDISK.SYS to permit it to be used with
DOS 3.3. I have only been able to test it with PCDOS 3.3 but I
think there will be no problems with any other versions of MSDOS.
The basic idea is to alter the DOS version check from 3.20 to
3.30. "20" is 14H, and "30" is 1EH - we need to change the
compare instruction at 5B8H in RAMDISK.SYS from "14" to "1E" To
do this easily, get DEBUG and RAMDISK.SYS on one disk and log it
in - a:, b:, or whatever. Then you type -
debug ramdisk.sys {calls DEBUG and loads RAMDISK into it}
nramdsk33.sys {changes the file name}
e 5b8 1E {makes the substitution}
w {writes out the new file}
q {quits DEBUG}
You should now have a new file - RAMDSK33.SYS - which you can
use in CONFIG.SYS under DOS 3.3 just as you used the old
RAMDISK.SYS under DOS 3.2. The version of RAMDISK.SYS for which
this patch is valid is dated 9/10/87 and has 6728 bytes in it.
For other versions, if there are any out there, the same patch
could be used, but you may have tofind the correct location. What
you are looking for is a compare instruction - CMP AX, 0314. The
hex bytes for this instruction are 30 14 03 - so if you can find
that, try changing the 14 to 1E as in the patch above.
The more difficult problem with PCDOS 3.3 is that FORMAT
will only format to 40 tracks rather than 80 and that it doesn't
read the 1400LT time clock properly on boot-up. I'd be glad to
learn of any solutions to those problems.
Robert Jacobs