mwilson@crash.cts.com (Marc Wilson) (02/18/90)
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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