Date   : Mon, 12 Feb 1990 23:59:59 GMT
From   : pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!lavaca.uh.edu!uhnix1!sugar!splut!jay@tut.cis.ohio-state.edu (Jay "you ignorant splut!" Maynard)
Subject: MOVCPM has copy protection

In article <9719@spool.cs.wisc.edu> tonyrich@titanic.cs.wisc.edu (Anthony
Rich) writes:
>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.)

>As a result, you can't run MOVCPM to generate a new copy of your CP/M
>while running someone else's copy of CP/M.

This is not intended as copy protection; it's intended to prevent MOVCPM
from building a garbage CP/M image.

MOVCPM uses a bitmap to determine which bytes to relocate when moving
the CP/M image. This includes the BIOS area as well as the BDOS and CCP.
The original intent was that you'd MOVCPM 54 (or whatever...it's been a
looo-o-o---oong time :-), then SYSGEN the resulting image, and then
boot. Each licensed CP/M distributor had utilities that built the MOVCPM
program from his customized image. For those of us who had to install
our own BIOSes, you had to MOVCPM, then load the BIOS on top of that,
then SYSGEN and boot.

The "Synchronization error" message is produced when the resulting
image, because of a difference between the systems, would have the wrong
bytes relocated, and therefore would be garbaged.

Nobody had even *thought* of copy protection when MOVCPM was
developed...

-- 
Jay Maynard, EMT-P, K5ZC, PP-ASEL   | Never ascribe to malice that which can
jay@splut.conmicro.com       (eieio)| adequately be explained by stupidity.
{attctc,bellcore}!texbell!splut!jay +----------------------------------------
                             Free the DC-10!


End of INFO-CPM Digest V90 Issue #24
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