chriswhit Posted December 25, 2009 Share Posted December 25, 2009 I have a 7800 dev system and a home built 48KB RAM Cart. My question is can a bigger ram cart be built? If so is there any info on this floating around? Thanks Quote Link to comment Share on other sites More sharing options...
jaybird3rd Posted December 25, 2009 Share Posted December 25, 2009 Good question. Anything larger than 48K would have to be bankswitched, and I don't think building a bankswitched RAM cartridge is as simple as replacing the ROM with an SRAM chip. As I recall, 7800 bankswitching is controlled by writing the bank number into the ROM space, but this would change the contents if that space was writable (as it would be with a RAM chip in it). In addition to that, I doubt DevOS is currently set up to write to such a cartridge, since none currently exist. I'd love to see more support for the XBoard, which adds 128K of RAM to the system in addition to a POKEY chip. That would be ideal for game development/testing, since it would eliminate the need to have RAM/POKEY on the cartridge. Granted, you'd have to modify the game for a standard cartridge when it's finished, but that wouldn't be too difficult. Quote Link to comment Share on other sites More sharing options...
chriswhit Posted December 25, 2009 Author Share Posted December 25, 2009 Good question. Anything larger than 48K would have to be bankswitched, and I don't think building a bankswitched RAM cartridge is as simple as replacing the ROM with an SRAM chip. As I recall, 7800 bankswitching is controlled by writing the bank number into the ROM space, but this would change the contents if that space was writable (as it would be with a RAM chip in it). In addition to that, I doubt DevOS is currently set up to write to such a cartridge, since none currently exist. I'd love to see more support for the XBoard, which adds 128K of RAM to the system in addition to a POKEY chip. That would be ideal for game development/testing, since it would eliminate the need to have RAM/POKEY on the cartridge. Granted, you'd have to modify the game for a standard cartridge when it's finished, but that wouldn't be too difficult. I'm ordering an Xboard. Will I have to take it out to run games with a pokey? Quote Link to comment Share on other sites More sharing options...
+Mitch Posted December 25, 2009 Share Posted December 25, 2009 Graham Percy designed a larger RAM cart for the DevOS system. Unfortunately, his website is no longer up. I think this is the last version of the instructions. You also need to email Eckhard for the updated software to go with it. Mitch devcarts4.pdf 1 Quote Link to comment Share on other sites More sharing options...
chriswhit Posted December 26, 2009 Author Share Posted December 26, 2009 Graham Percy designed a larger RAM cart for the DevOS system. Unfortunately, his website is no longer up. I think this is the last version of the instructions. You also need to email Eckhard for the updated software to go with it. Mitch That is an awesome post the info is far better than what I hoped for. Thank you Quote Link to comment Share on other sites More sharing options...
jaybird3rd Posted December 26, 2009 Share Posted December 26, 2009 Graham Percy designed a larger RAM cart for the DevOS system. Unfortunately, his website is no longer up. I think this is the last version of the instructions. You also need to email Eckhard for the updated software to go with it. Wow, thanks for posting this! I hadn't heard of these designs before, but it looks like he successfully implemented bankswitched RAM. I've got some seven-hundred C300565 boards at my disposal, so I'm going to try building some of those cartridges. Thanks again! Quote Link to comment Share on other sites More sharing options...
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