At 19:23 05.05.98 +1000, you wrote:
>I'm asking if the ROM addresses could also be writeable, given a correct
>cartridge? I know I should figure this out myself, but asking is just so
>much easier.
There is no read/write select line on the cartridge port. You
can either use one of the address lines instead, which would
reduce the size of theavailable RAM by half, or you could
implement a much more complicated way of writing like it was
done in the Supercharger.
>My current plans for speed, by the way, involve placing self-modifying code
>in zero page to help me whizz the kernel along. Yeah, I know space is
>tight. Just wondering if anyone has done this kind of thing. Last time I
>asked that, the answer was "oh... about 1000 people".
I have used self-modifying code in Supercharger RAM and in zero
page RAM in some of my programs. The space in the zero page is
very small. It allows only display routines, that use only one
trick like this throughout the entire screen.
If you really want to push the VCS that far, you should start
nagging Chris Wilkson to finish his mega cart. :-)
It is supposed to provide 128kb of ROM and 32 kb of RAM,
which can be switched in as 1kb banks. (RAM is only 512 byte,
since half of the address space is used for write and half is
used for read.) That should provide enough RAM for self-modifying
code.
Ciao, Eckhard Stolberg
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