Date   : Sat, 17 Feb 1990 20:28:17 GMT
From   : crash!mwilson@nosc.mil (Marc Wilson)
Subject: MOVCPM fix

     Here is the ultimate solution to the MOVCPM problem.  Disable the serial
# checks entirely.  I'm surprised that no one has suggested this yet.

     I had to do this a long time ago, when I replaced DRI's BDOS with one
of the PD replacements, and needed to run MOVCPM to generate a bootable
floppy.

     Note that this information is specific to a particular copy of MOVCPM.
Your patch point is almost guaranteed to NOT be in the same place.  But, in
looking at over a dozen copies of MOVCPM from as many manufacturers, I found
that:

       1) The code around the patch point always looks the same ( that
          portion is DRI's, not the vendor's )

       2) The patch point has always been within 80h bytes of the point
           specified in this file.

     Also... I did NOT write this patch.  I found it on a local BBS, MANY
moons ago.  It's not my fault if you screw up your copy of MOVCPM.  Do
NOT do this on an original disk!

MOVCPM.FIX:


   I recenly tried to help a friend generate a new system
on my machine, using his copy of MOVCPM,and we were greeted
with, "SYNCHRONIZATION ERROR" followed by the machine quiting.
After talking to another friend, I was informed that the
problem was caused by a serial number mismatch between my
system and his copy of MOVCPM. My friend further stated that
there was "NO WAY" around this protection. After pondering the
problem a while I decided to start disassembling MOVCPM with
the help of the "L" command in DDT. What follows is the
result of my efforts.

Begining at 2C0 I found the following code:

-L2C0 
02C0   POP     D
02C1   LXI     D,1200
02C4   LHLD    037A
02C7   MVI     C,6
02C9   LDAX    D
02CA   CMP     M
02CB   JNZ     025A
02CE   INX     H
02CF   INX     D
02D0   DCR     C
02D1   JNZ     02C9

I then did the following substitutions:

-S2CB
02CB C2 00
02CC 5A 00
02CD 02 00
02CE 23 .


After the above changes do a SAVE 40 MOVCPMNU.COM and you have
a version of MOVCPM that will run on any machine.

   With the above changes under my belt I decided to do some
more poking around in MOVCPM.COM and came up with the following
addresses that might arouse your curosity.

       B5F,    1200,   D28

       Best of Luck,

                       A HACKER

-- 
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Marc Wilson
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