Vampire, Gotek, 68000, misteries, doubts, questions...

[guest11527]

Starting with the 040 opcodes and addressing modes were dropped to simplify the instruction set.  The 060 could not do a 32b by 32b multiply, for example.

Well, the addressing mode that is missing is actually "packed decimal", which is a 68881/882 addressing mode. 64 bit integer instructions are missing, yes.

But "complexity" is not a matter of the number of instructions. The 68060 is certainly more complex than the 68020, given that it includes "one and a half" arithmetic unit, is super-scalar, includes the FPU and MMU, unlike the 68020 which micro-coded many instructions.

The 68000 is, for example, completely micro-coded, i.e. it runs on its on native "microcode" that interprets the 68000 instructions.

[grond]

But "complexity" is not a matter of the number of instructions.

I obviously was referring to the ISA, not the complexity of the circuit. Obviously more recent processors tend to be more complex than their predecessors. This already because the number of transistors is growing exponentially. Did I use the word "obvious" already?

[guest11527]

I obviously was referring to the ISA, not the complexity of the circuit.

In terms of the ISA, the 68020 together with the 68882 and 68581 is the "most complete" processor from the 68K line, certainly. It also includes the ring-protection mechanisms - which probably nobdoy ever used at all.