I'm a big fan of hacking 8 bit Ataris (I even have one 130XE with a 63B09 in it).
But the gpu steals cycle from the cpu in that design, making the difference between a 1 MHz "breadbox" and a 1.78 MHz Atari negligible.
That's likely true. The Atari 8-bit are an older design, and it shows in some cases. Yet, it is a fascinating design whose second edition became the Amiga.
It is curious that the 68000 doesn't access memory any faster (just over a larger bus), what the 8 bit cpus do in one cycle, the "better" cpu takes four cycles to accomplish.
The 68000 is a fully microcoded CPU, i.e. every instruction is executed by the microcode engine and hence takes several micro-code instructions to complete.
The 6502, however, is completely hardwired silicon, and hence does more work per cycle. With the known defects the simple 6502 design caused, namely instructions with unknown side effects, unimplemented instructions and instructions that hang the CPU completely. Motorola changed this for the later members of the family, i.e. many instructions in the 68060 are also hardwired (with some errata in the early masks due to the complexity of the design).
I kind of miss the 8 bit stuff (except for that 64K address limitation).
You can still program and run programs on the 8-bits, of course. I'm working with the ca65 assembler and the Atari++ emulator. Works quite nicely.
