Re: Sinclair QL wasn't 16 bit...nope, wrong on 68k family
This is how it actually was. Working on the bare iron.
As long as all address pointers were 32 bit clean (no sticking stuff in top 8 bits like the original MacOS 64K ROM Memory / Resource Managers did) code written for the 68000 in 1984 could run unmodified on all future 68K processors and emulators. As all i/o was memory mapped the main difference between the 68000 and 68008 was the 68008 took twice as many clock cycles to read / write. That's all. Assuming the standard number of wait states for the RAM on the motherboard of course.
For 68k asm programmers the CPU model you wrote for with the 68040 was exactly the same as the 68000. For 99%+ of your code. Same regs, same instructions The only real difference was added FPU/MMU instructions and low level exception handling was more much complex. Although you could roll your own soft-coprocessor with the '20 and later. So add your own instructions. The other use of F traps. Not just MacOS API calls.
Unless you were doing system level code the 68040/60 instruction set was pretty much the same as the 68000. The initial instruction set was so well architected.
So.
68000 was 32 bit address, 32 bit data regs / 16 bit data bus, 24 bit address bus
68008 was 32 bit address, 32 bit data regs / 8 bit data bus, 24 bit address bus
68010 was 32 bit address, 32 bit data regs / 16 bit data bus, 24 bit address bus - handled address exception continuations correctly, had barrel shifter
68020 was 32 bit address, 32 bit data regs / 32 bit data bus, 32 bit address bus - full support for coprocessors, MMU etc
68030 was 32 bit address, 32 bit data regs / 32 bit data bus, 32 bit address bus - on board MMU, instruction cache
68040 was 32 bit address, 32 bit data regs / 32 bit data bus, 32 bit address bus - on board MMU / FPU
The width of the data bus only effected data move clock cycle count and the 24/32 address bus was only of interest to hardware designers.
Based on way too many thousands of hours in 68k asm land from 1984 to late 1990's.