Re: [stella] smart multicart

Subject: Re: [stella] smart multicart
From: emooney1@xxxxxxxx (Erik K Mooney)
Date: Mon, 25 Aug 1997 18:22:36 -0400
>Ok, now I have this thing in mind... please forgive me if it's a crap 
>idea,
>I know just a little of electronics.
>
>Could a joystick port be used to switch banks of Rom memory? (remember 
>that
>the joystick ports can be set for output.)
>
>Imagine a cart with a 64K Eprom, address lines 0-11 go to the VCS, and
>12-15 to a DB9 connector plugged into the Player 2 joystick port (some
>pull-down resistors could be needed).
>
>Each 4K bank would begin with the code to switch to the first bank 
>(for
>bankswitched games), or to the bank with the game select menu (for a 
>multi
>cart use). The VCS would switch banks writing to the register that 
>controls
>the pins of the player 2 joystick port.
>
>Pros: minimum extra hardware needed
>Cons: you lose one joystick port :)
>
>Is this a totally inpracticable idea?

As someone else said, when you switched to another game, it would
initialize
the joystick ports, and you'd lose your bank setting.  I suppose one
could
modify the code for each game to not initialize the DDR for the second
joystick
port; then, as long as the game doesn't try to output to the port (none
should
except Video Touch Pad games), it will work... though you're limited to
one-player games (two with paddles.)

I see possibilities to develop a standalone cart this way... that pretty
much provides
bankswitching for a ROM up to 64k, and the hardware would likely be
simpler and
cheaper (?) than Wilkson's 128k cart design.  

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