apersson850 Posted October 30, 2019 Share Posted October 30, 2019 (edited) Putting it in the expansion box doesn't work. You'll not get the 16 bit wide memory bus, so you don't get the speed advantage. Also it's not doable at all, since my design sits inside the console's memory decoding logic. It has the ability to hijack the console's access to everything, including operating system ROM, cartridge memory - anything. You can even overlay memory across the internal RAM PAD, sound chip, VDP chip, speech etc. It will kill access to all these functions, but you can use that 8 K bank as a buffer for something, when you don't need to update the screen, play sounds or anything else like that. So the advantage is that you can have contiguous RAM across 64 KBytes, provided the data/code you have at certain locations doesn't have to be available all the time. You have to turn some of it off to access disk drives, video display etc. But you can copy the console ROM into RAM, then modify interrupt vectors, the GPL interpreter - well, everything. I have a program which makes a RAMdisk of these 64 K, plus the memory in a GRAM Kracker/Maximem module. You could make a game that has an elaborate AI, all in assembly, which can run in, say, 32 K of fast RAM, then with a single CRU instruction, you disable that memory and get the standard console back. But the content of this 32 K is still there, so the next time it's the computer's turn, you execute one CRU instruction and have it all back again. I'm not saying this just because it's my own design, but it's actually the most versatile memory expansion scheme I've seen for the 99/4A, which also allows a 110% performance upgrade (if you run both workspace and code in normal expansion RAM, compared to both in fast memory). Some other designs are close, but they didn't have the imagination to make the bank switching software controlled, but use manual switches instead. Or they have much more memory, but access it only through a porthole like 4 KBytes wide or so. The big disadvantage with my design is that it's tricky to install. Just imagine if TI had done that from the beginning... Edited October 30, 2019 by apersson850 Quote Link to comment Share on other sites More sharing options...
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