Subject: Re: [stella] Megacart Specs|
From: Chris Wilkson <cwilkson@xxxxxxxxxxxxx>
Date: Sun, 12 Apr 1998 18:26:24 -0700 (PDT)
> > On Sun, 12 Apr 1998, Chris Wilkson wrote: > > RAM (see below). You could use 3K blocks for ROM and permently map RAM > > into the remaining 1K, but that either wastes ROM space or the decoding > > gets nasty from a hardware point of view. > > Small games, okay, but it just seems that if you've written a game that > uses the full 128K of ROM code (a huge kernel and tons of date) and you > have only 1K linear ROM available at a time that the programmer is going > to have to bank switch constantly to get anything done. The percetage of > bankswitching code to useful code is starting to get really wasteful. > > After you load the 1K chunks, can you run a program linearly across the > loaded banks without bit-twiddling? If so, then it's not too bad because > you could write code as de-facto 3K chunks and then swap three banks in > and out that way but I don't know why a program would need to be broken > down into even small chunks. Yes, as far as the 2600 is concerned it simply has a 4K chunk of memory at at a given time...except when there is RAM mapped into a slot. Then you lose 512 bytes because of using A9 for a read/write line. If you wanted to, you could even execute code from RAM and just keep going linearly into a ROM block. But you can't do the reverse...the write port for RAM is in the lower 512 bytes of the slot. If you try to execute linearly into a RAM block, you'll overwrite the RAM! -Chris the code. -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/stella.html Don't post pirate BINs to Stellalist. Be a programmer, not a pirate. Write the best game, win framed autographs of famous Atari alumni!!