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From: Lion (all posts)
Date: 1998-05-18
Subject: lost mail 2, "re:tapes!" from Martijn van Buul

Martijn writes:

Marko Mäkelä wrote:

> Just type L in TEDMON and press STOP when the FOUND message appears on the
> screen. Then change the loading address in the tape buffer ($33c or
> something) and continue loading by replicating the necessary code from the
> ROM in RAM. Sorry, I don't remember details, but I successfully copied
> some tape games a couple of months ago.
Did that, done that, been there before. Didn't work because...

> There was one turbo loader (maybe by Anirog) that was very difficult Guess who published "Moon Buggy C16" ? Indeed: Anirog. I'm starting to think that the loader is niftier than the actual game.

> and
> I gave up. Part of the loader code will be in the tape buffer, and the
> rest will be loaded to $2xx

$020F. Tried to relocate it to $120F, but to no avail. Somehow, it seems to crash the load-subroutine in ROM, making it restart, thus interpreting the block it last read as a header. FYI: if you halt the loading process after it found the header and enter 'load' again, load will stop with a syntax error (!?) after it has read from tape for a while.

> so that it will overwrite the beginning of
> the tape buffer. The program will autostart, and the program starts with
> a loop that uses the undocumented DEC+CMP instruction to decrypt the rest
> of the program. It depends on the CPU register values set by the ROM
> routines. If I had had more time and a blank tape, I would have written a
> program that is equally big and ends in the same bytes, but stores the CPU
> registers when started.
Darn. Guess the World has to live without Moon Buggy :)

>
> > I guess I'll have to dissassemble the C64 SETLFS in order to be sure,
> > but that involves a serious rearangement of my desk :)
>
> The SETLFS and SETNAM routines just store A, X and Y to some zero page
> locations and exit.
Yeah. I know. But they seen to behave differently on a C64 than on a Plus/4

--
Martijn van Buul, martijnb@mud.stack.nl Tijntje@OuterSpace - 131.155.141.166 3333