Quote:
Emulation mode was devised to satisfy an Apple requirement that the '816 be adaptable to the ][c and ][e designs. It makes no sense to use the '816 as a 65C02 in a fresh design.
Yes, they had to keep full backwards compatibility with earlier Apple II models, something that's irrelevant if you're building your own
non-Apple-II computer. One might want to initially leave the '816 in emulation mode to test out part of his board with what acts like the familiar 65c02, and in fact I'm still running older 65c02 Forth software on my '802 too. But when the builder/programmer who does a lot of assembly language sees the advantages of the extra instructions and addressing modes, switchable 8/16-bit registers, reduction in the number of instructions needed to do a lot of things, relocatable zero page, unlimited stack for local environments, etc., he'll be hooked. Address bits 16 to 23 are not needed to gain these advantages.
BigEd wrote:
Are you quite sure that emulation mode is incapable of high addressing? That isn't my understanding.
There's too much to write here, but the differences are found in the
programming manual starting on page 58. Many of the '816-only instructions can be used in emulation mode too, but if you take advantage of them, the code won't run on a 6502 anyway; so you might as well go into native mode and enjoy the '816 as an '816.