10/28/2022 0 Comments Raspberry pi 3 classic mac emulator![]() ![]()
Luckily, unlike the Mac, the Lisa's (68000) ROM isn't used for much except the POST (Power On Self Test) and booting. As such another memory area register can be changed to "page" through the various memory areas. The video circuitry is fairly simple - a dumb frame buffer that shares its memory with the Lisa's memory space. 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 linearly. ![]() One lives in offset of two bytes, the other in an offset of 4 bytes. For example a memory parity error detector, a video scan line interrupt, and the MMU. To make things even more complex, there are special memory addresses that turn on or shut off various flip flops. dual parallel port cards for access to Profile drives On older Lisa's there's also a socket for an Amd 9520 #Raspberry pi 3 classic mac emulator software(In the Mac, the mouse is software driven.) Additionally, the I/Oīoard also has a 6504 CPU with it's own ROM to drive the floppies/twiggy drive.
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