Re: Copy Protection of PET cassettes - Flash Attack.

From: Anders Carlsson <>
Date: Tue, 10 Aug 2010 16:10:15 +0200
Message-ID: <012001cb3895$c1971e20$>
Daniel Kahlin wrote:

> Anyway a quick analysis shows that the game loads $027A-$2000. The first 
> chunk at $027A looks like a cassette header indicating a file "FLASH 
> ATTACK" $03FD-$2000

Bill Degnan wrote:

> Yes.  Now try to save this to cassette using the TIM prompt using standard 
> procedure.  Something prevents dumping the memory to tape.

While I haven't studied the PET memory map recently, isn't $03FD part of the 
cassette buffer? If so, perhaps the computer rebuilds that part of memory 
when you save in a normal way, and you lose whatever was there.

I remember on the VIC-20, there was a trick you could use to copy programs 
which had content in the cassette buffer. With respect I might remember 
certain details wrong, it looked something like this:

A$="" : FOR I=833 TO 1023 : A$=A$+CHR$(PEEK(I)) : NEXT

The FOR loop thus would create a string consisting of the content of the 
whole cassette buffer. Might be worth examining?

Best regards

Anders Carlsson

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Received on 2010-08-10 15:00:30

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