Dave Walker wrote:
> Rich,
>
> I once looked into this. The copy protection itself is easy enough to
> break - if I remember correctly it was based on reading some hidden
> sectors from the microdrive. The issue was that it had to be read into
> a specific address in memory and executed from there - and the address
> in question only seemed to work on an unexpanded QL.
This sounds very much like the protection on Paraoh (right name?) - where
you had to navigate through a purple(ish) maze with egyptian style music in
the background, avoiding naties like snakes. A bit of code was loaded from
a hidden file (the directory had to be changed before it could be loaded,
and changed again afterwards to rehide it) into the base of the screen
memory ($20000) where upon it was called.
If anyone has managed to get Pharoah to run from disk without being memory location specific, please send me a copy as I have the rights to sell it again!! I have tried, and failed miserably.
Maybe Ergon could provide the source for the program they wrote to overcome the problems with Psion Chess being location specific (Davide??)
Psion Chess _WAS_ position dependent and the boot program RESPR'd lots of
memory to get the right address - if my memory serce me right it used the
same protection method (seactor header) as The Pawn...
> I might have to
> dig out my copy and see (assuming it still works) whether anything
> better can be done.
It loads as a RESPR (a=RESPR(001024):LBYTES mdv1__,a:call a) and it uses the
cartridge random ID number from the header of each sector (got via vector
12A). If the ID on the key cartridge matches the required number, it then
continues with the boot program (OPEN_IN#3,"mdv1_ ":FLRUN) - if the ID
didn't match it reset the machine. The code loaded (mdv1__) contains the
code for FBOOT, FSAVE and FLRUN.
It's very easy to break...a little modification to the check (2 m/c
instructions) will suffice - I can dig out the details of a change, if you want.
That bit is dead easy to overcome yes, and for a while I had the main program for QL Pawn loading off disk - the problem was the data microdrive if I recall this correctly - bits of the adventure were loaded from specific microdrive sectors methinks!!
Rich Mellor
RWAP Software
7 Common Road, Kinsley, Pontefract, West Yorkshire, WF9 5JR
TEL: 01977 614299
http://hometown.aol.co.uk/rwapsoftware
