The problem with the 16-bit micros in the early 80s — such as the Motorola 68000 (used on the Mac) and the Intel 8086 (used for IBM PC compatibles) was not just cycle time but also the fundamental difference between being able to stick “hardware like functions” (such as a byte code interpreter, graphics painting, music, etc.) into a microcode... See more

The Alto was fabulously efficient because its approach to how its real CPU (the microcode engine) interacted with the available memory bandwidth (including the use of multiple program counters for zero overhead low-level task switching and avoiding interrupts).

Whereas the commercial CPU architectures had very poor notions of how to use memory and... See more