Designing around a 6502 (was Re: Assembly on a Apple IIc+)

On Sat, 8 Feb 2003, Jim Keohane wrote: This gives me awfully devious ideas... First, were there any 'multitasking machines' designed around the 6502? If you wanted to do multitasking, it seems like you could design a fairly simple MMU that would swap out the zero-page and stack (or all of the memory pages) for different ones, depending on the running task. Leaving only a few registers that need to be saved, it would leave a very small overhead for task swapping. You could even implement kernel and user mode into the MMU, making it swap pages automatically on an interrupt or 'memory write' to signal a syscall (and a swapping of pages, interrupt to the CPU and transition to 'kernel mode'). I think I'm going to need to start playing with designing a 6502-based machine now... Or maybe I should just get back to working on putting machines into racks so I have some floorspace around here to work in. Pat -- Purdue Universtiy ITAP/RCS Information Technology at Purdue Research Computing and Storage http://www-rcd.cc.purdue.edu