Motorola 68000 Microprocessor
68000 was the best of the CISC microprocessor designs.
Architecturally, 68000 was a 32-bit CPU,
as its registers were 32-bits though its data bus was 16-bits.
Although a CISC design, its instruction set was lucid and utilitarian.
Its instruction set was considered orthogonal because
all addressing modes were available to most instructions.
It had a 32-bit flat memory model. Had a 24-bit (16MB) physical address space.
Privilege level model was simple. Difference in supervisor mode
was a supervisor SP and access to interrupt controls.
68000 register model was simple:
D0..D7 data registers
A0..A6 address registers
A7/USP stack pointer (user mode)
A7/SSP stack pointer (supervisor mode)
CCR flags register
As 68000 architecture was designed right from its beginning,
it did not change fundamentally across generations (68000, 68020, 68030, 68040, 68060).
I ran my own benchmark code on a 68040 Amiga and 80486 PC, and 68040 was much faster (twice IIRC).