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From: SLSW2@cc.usu.edu (Roger Ivie)
Newsgroups: comp.os.cpm
Subject: Re: MOVCPM has copy protection
Message-ID: <18399@cc.usu.edu>
Date: 13 Feb 90 02:15:45 GMT
References: <1534@shell.shell.com> <9719@spool.cs.wisc.edu>
Distribution: usa
Lines: 32

In article <9719@spool.cs.wisc.edu>, tonyrich@titanic.cs.wisc.edu (Anthony Rich) writes:
> In article <1534@shell.shell.com> svh@shell () writes:
> 
>>I have recently gotten together an 820-I with 8" drives, and would like to
>>do some stuff that would require me to MOVCPM down a couple'o K. The
>>problem is, that the version I have will generate "Synchronization error"
>>every time.
> 
> According to the book "Inside CP/M" by David E. Cortesi, MOVCPM has a kind
> of copy protection built into it.  When it starts up, it does some
> checking to see whether the copy of CP/M you're trying to generate with
> MOVCPM matches the copy of CP/M you're currently running.  If not, it
> displays the message "Synchronization error" and quits.  (I'm not sure
> what it actually tries to match.  I think it does some kind of checksum.)

Rumor has it that MOVCPM compares the serial number of the CP/M that 
you're trying to move with the serial number of the CP/M that you're
running.

The serial number is stored in two places in CP/M: the first is just
before the BDOS, and the other is near the command line buffer in the
CCP. I'm not certain which one MOVCPM is checking. You should be able
to zap the serial number in MOVCPM's image using DDT, although I've
not tried it.

===============================================================================
Roger Ivie

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(801) 752-8633
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