> 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.
Sort of. There is no read/write line to the cart slot; if you have a
cart with RAM, you have to use one set of addresses to read and another to
write to the same block. (ie, 512 bytes of RAM might be read at addresses
$1000 to $13FF, but read from $1400 to $17FF) Other than that, you can
write to any address, but there of course must be physical RAM there or
your writes aren't going to do anything :)
> 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've done it, though I don't know how many other people have. Mine was, I
think, a 46 byte routine that drew six lines of sprites, using
DEY/BNE/WSYNC, and ending with a RTS. (it was only called from one
spot in ROM, but RTS is two bytes smaller, albeit two cycles slower, than
JMP absolute.)
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