c65 Software Development


@rosettif Actually, M65 boot into "C65" so no need for "GO65". If you think about the extra features M65 provides you need to enable VIC-IV I/O mode first, so you can access the extra I/O registers and features needed for M65-specific things (what I can see here: actually M65 is a greatly enhanced C65, so it's the logical step in my opinion, even the case is planned to be C65-like). You can say - for sure - to switch into C64 mode though, with "GO64" which was also part of C65. That has several problematic aspects on a real C65, for example the read-modify-write opcode works different (which is one of the major C64 compatibility issues, eg the well known trick to acknowledge VIC interrupts on C64 based on the RMW behaviour), also the timing of VIC-III is different (and one of the most interesting part: as far as I can remember, VIC-III changes mode only at the end of a character line). Oh yes, and the different CPU, lack of "illegal opcodes" etc. Again, I can say, that in my opinion it's kind of nice that these can be "cured" on M65 at least, to have a better (even if not perfect) C64 mode than C65 could provide (that's nothing compared to the C128's C64 mode of course). But the important point here, that an M65 behaves like a C65 after booting. Though, still, to be able to use M65 (or an emulator) you still need to attention to provide the system needs which is one thing over a real C65: mostly the SD-card stuff so that M65 can "boot" at least. For Xemu I plan here to create an SD-card image file (and making it default) if it cannot be found and no option is given to use some other non-default one. With this, the preparation work is not so much different than any other emulator, there you need to get ROMs (for example a C64 emulator) as well, anyway!


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