Re: Additional cartridge ROM question

Re: Additional cartridge ROM question

From: Jim Brain <>
Date: Wed, 25 Mar 2009 22:03:16 -0500
Message-ID: <>
Marko Mäkelä wrote:
> On the C128 MMU, EXROM and GAME are general purpose input/output pins.
> In C128 mode, you can use them as outputs: the PLA doesn't care about
> them.  If you programmatically switch to C64 mode, you can set EXROM
> and GAME as you wish, but you can't control them afterwards, since the
> MMU won't be addressable in the C64 mode.
So, as I understand this, in order to make a cartridge that supports 
128mode, I need to put the ROM /CE on one switch (to bank it in an out), 
and EXROM (and game) on another switch, in order to force 64 mode (or 
for use on a real 64).

I wonder if that should also be reflected on an address line on the 
EPROM, so different boot roms get mapped in depending on machine mode 
(128 versus 64)


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Received on 2009-03-26 04:41:32

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