Subject: Re: [stella] just wondering From: Erik Mooney <emooney@xxxxxxxxxxxxxxxx> Date: Tue, 5 May 1998 09:37:48 -0400 (EDT) |
> 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.) -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/stella.html
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