RE: New Carts
Date: 2001-11-01 07:50:11

Hi Marko,

Will see if I can configure a dual EPROM cart with a switch on the GAME
input. The upper ROM can call the lower one's cold vector. The RAM test will
fail after the first 4k, but with a flick of the switch the normal config
will be possible. I'll put a copy of the Kernal in the upper ROM just in
case the car needs if for "printing" etc... Hopefully it doesn't need the
BASIC ROM routines.

- Nick

>> >Since it is intended to test ROM, RAM, and I/O, there is no point
>> >in the Ultimax mode and then switching.
>> Except to maybe an idiot like me, if it has a black screen before and
>> the cartridge gets inserted I am no wiser as to whether its something
>> like the Kernal rom or a reset problem :)

>Exactly.  The KERNAL ROM routine executes one RTS instruction before
>jumping to the cartridge code.  If the RAM at the top of the stack area
>(somewhere around $1f0-$1ff) is broken, executing the RTS may fail.  As
>there are numerous other reasons for the screen remaining black, the
>starting method applied by the cartridge is not very useful.


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