Date   : Mon, 12 Feb 1996 14:13:31 +0100
From   : Robert Schmidt <robert@...>
Subject: Re: Decoding BBC tapes... 

>... but be aware that many of the protection schemes used on commercial
>software do wierd things such as invert the data bytes, XOR them with some
>other value etc. to ensure that a stardard *load etc. will FAIL with
>CRC errors.  The program loaders hook an event (sorry, I'm trying to
remember
>this but have no docs to hand) so that they can invert the bitstream when
>loading (in a manner similar to a DOS TSR IIRC).

I guess reading the tapes "manually" (outside of the OS) will preserve
whatever protection mechanisms there are.  However, none of the emulators
I've seen so far emulate a "real" loading of tapes, i.e. blockwise (BeebEm
reads files from disk images, Xbeeb reads them from an emulated file system
hosted in UNIX), so I guess these will be beaten by such protection?

robert

--
Robert Schmidt - robert@...         - http://www.idt.unit.no/~robert
	
	Maintainer of "The BBC lives!" page:  
	http://www.idt.unit.no/~robert/bbc/bbc.html