Yeah, that upper 8-bit address tagging thing was a "clever"... waste of cycles. Just rotating/shifting 32-bit registers by 8 places costs 24 cycles (8 + 2 *

Yeah, that upper 8-bit address tagging thing was a "clever"... waste of cycles. Just rotating/shifting 32-bit registers by 8 places costs 24 cycles (8 + 2 * n) on 68000, like if the value was passed in a register. Shifting the value by 24 places is even worse, massive 56 cycles... You could also do "move.b (a0), d0" directly from the pointer to pointer address. That'd cost just 8 cycles. Self-modifying code wasn't all that beneficial nor popular on 68k because of ample number of usable registers, 16, including a7, that is used as a stack pointer, but nothing prevented you from using it for something else for a while. I think copy protections and such used weird tricks like SMC. Machine code generators (kind of limited JITs) were useful, but those usually generated large enough blocks of code to flush a small cache by default. There were also some race conditions with DMA (like blitter and perhaps with disk), when DMA completion wasn't properly checked. But 99%+ of code didn't use those tricks and was perfectly compatible.