why the 65816

Post date: 21-Dec-2009 00:00:22

For anyone obsessed with the 6502, the 65816 brings some welcome headroom: a 24bit address space, a second 8-bit accumulator, or 16-bit modes for accumulator and/or index registers. Also allows for relocating zero page and the stack. And it clocks a lot faster than 80's-era 6502s. Most importantly, in 40-pin form it's almost pin-compatible.

But there are downsides: the memory is banked rather than flat; the multitude of operating modes can be confusing; the zero page and stack, and the various vectors, all have to be in bank 0. (It's easy to avoid these: pick an operating mode and stick to it; place all your code in one or two banks and use the rest for data - or stick to a 64k memory space.)