2022.04.01 : Released the 4th Release Candidate of 1.2.7 here . 2020.08.24 : Released the 3rd Release Candidate of 1.2.7 for macos X + source here . 2020.08.03 : Released the 2nd Release Candidate of 1.2.7 for macos X + source here . 2020.06.05 : Released the 1st Release Candidate of 1.2.7 for macos X + source here . 2019.11.11 : Released the first beta version of 1.2.7 for macos X + source here . 2020.04.12 : Released the second beta version of 1.2.7 for macos X + source here . 2019.11.11 : Released a 2nd
To make things even more complex, there are special memory addresses that turn on or shut off various flip flops. For example a memory parity error detector, a video scan line interrupt, and the MMU. The VIA's are not identical in access. One lives in offset of two bytes, the other in an offset of 4 bytes. The 6504's 1024 bytes of memory is battery backed up (this is what the four NiCAD AA's on the I/O board are for.) The 6504's address space is available to the 68000, but in two byte skips as opposed to li
The video circuitry is fairly simple - a dumb frame buffer that shares its memory with the Lisa's memory space. As such another memory area register can be changed to "page" through the various memory areas.
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