Subject: RE: [stella] Perfect BIN copy protection From: Nicolás Olhaberry <nolh@xxxxxxxxxxxxx> Date: Sun, 3 Feb 2002 16:35:46 -0300 |
----- Original Message ----- From: Chad Schell <gamer@xxxxxxxxxxx> To: <stella@xxxxxxxxxxx> Sent: Saturday, February 02, 2002 7:04 PM Subject: Re: [stella] Perfect BIN copy protection > The difference lies in the state of the processor flags and the 2600's > internal RAM. With a standard cart, when you plug it in and turn on the > 2600, the RAM will be in a random state. Are you sure about this? I think the RAM starts in a known state, zeroed, most likely. For example, combat uses the address $DD as some sort of mask for the objects colors (I can´t give more info, never looked at the code with too much detail). The game doesn´t write on $DD until you press reset or some time passes, so, for the first seconds of the game, $DD will have an undefined value, and, unless it is zero or one (since the low order bit isn´t used in COLUXX), you don´t get the right color for any object. Also, Roger Williams posted some interesting thoughts on how the "frying" worked, he said that the ram gets undervoltaged, and since the effect it´s so repeatable, the ram probably started in a known state. I tried this in my emu with a few games, and storing zero in all the ram area seems to produce the same "frying" effect. I didn´t get the same effect storing one, for example the guy in Pitfall! doesn´t get colored in black. Bye, Nicolás. ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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