You're right, I was simplifying. > The VIC-I chip can address 16K, but only internal memory, not on the > cartridge bus. Normally the operating system nearly all of the lower > 1K, but in certain demos like e.g. VIMM and VIMMII, Albert of Pu-239 > stored the video matrix in that area in order to use all of the 4K for > bitmap. (The unexpanded VIC-20 has 5.5K RAM in total of which 3.5K is > available to the user) It's largely impractical to put the screen matrix in the first 1k from BASIC. Although you could blank out areas you can't touch with a foreground colour that matches the background colour. Theoretically that could be supported too though. > Some individuals have installed internal 3K expansion to their VIC-20 > by piggybacking chips. It is highly non-standard, but allows the VIC-I > chip to access that memory as well. I suppose in theory one could > install internal 8K expansion and access that memory for the VIC-I > chip as well but I don't know anyone who has done it. vice only allows access in the standard locations } else if ((addr < 0x0400) || ((addr >= 0x1000) && (addr < 0x2000))) { /* RAM */ b = mem_ram[addr]; Theoretically you could hook 64k (or more) and then add extra banking bits (like c64 has). I think that is out of scope.Received on 2018-07-27 13:00:05
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