Path: utzoo!mnetor!uunet!husc6!bloom-beacon!mit-eddie!bbn!rochester!pt.cs.cmu.edu!andrew.cmu.edu!al1f+
From: al1f+@andrew.cmu.edu (Andy A. Lee)
Newsgroups: comp.sys.atari.8bit
Subject: Re: 16K cartrdige - How?
Message-ID: 
Date: 6 May 88 20:06:14 GMT
Organization: Carnegie Mellon
Lines: 22

Christopher,

Regarding your Centipede experiment, I can give you some assistance.  First of
all, there's a way to get around the RAM-vs-ROM protection schema: you built
yourself a 'blank cartridge'; a cartridge that grounds the 'read-only' pin of
the cartridge port.  You see, when the 'read-only' pin is ground, the Atari
won't write to its RAM where the cartridge resides ($A000-$BFFF) even though it
is RAM.  If you don't know where the 'read-only' pins are, let me know.  I will
look them up for you.  There are two 'read-only' pins in the left cartridge
port.  One is for $A000-BFFF, and another for $8000-$9FFF.

About 16K Cartridges, they come in different sizes and shapes.  For example,
one of the well known 16K cartridges, "Action!", has a 4K block of codes reside
in the Atari at all time while 3 other 4K blocks of codes are being switched on
one at a time.  They also called 'bank selecting' cartridge.  Although they
claim to be 'un-copyable', I have seen some hackers managed it by modifing a
256K 800XL to simulate the bank switching.

Although I don't do any Atari anymore, I still remember a lot from the old
days.  If you have any more questions, please don't hesitate to ask.

* Andy *