Examples of Different Implementations of Same ISA
80x86 ISA defined in 1978
Implementations are:
- 8086, 8086, 80186, 80286, 80386: Multicycle implementations; each successive implementation widened external data busses, increased external address space, reduced clocks per instruction
- 80486 : Pipelined implementation, also integrated Floating point unit on same die
- Pentium: Superscalar implementation, 2 instructions max per clock
- iA64 (Merced)? : > 2 instructions per clock