Instruction Set Architectures: RISC, CISC, & 64-bit Processors. CISC (Complex Instruction Set Computers). IA - 32. 1978: The Intel 8086 is announced (16 bit architecture) 1980: The 8087 floating point coprocessor is added 1982: The 80286 increases address space to 24 bits, +instructions
“adding new features as someone might add clothing to a packed bag”“an architecture that is difficult to explain and impossible to love”
“what the 80x86 lacks in style is made up in quantity, making it beautiful from the right perspective”
Although there are a variety of approaches taken to RISC architectures, certain characteristics are common to all of them:
Intel called this hack CRISC. This concept was so moronic that even Intel could not market it!
12 addressing modes:
8 addressing modes:
7 addressing modes:
5 addressing modes:
4 addressing modes:
Future innovation should come in micro-architecture enhancements and compatible extensions to dominant instruction sets, rather than the creation of new instruction sets.
Is the trend clear?
With ever growing software complexity and installed base the value of remaining compatible with and extending existing, dominant instruction sets heavily outweighs any disadvantages.
Is the time now?
Technology has passed the point where instruction set costs are no longer relevant.
Port thousands of applications, operating systems, drivers, codecs, tool chains and virtual machines
TodayArchitectural Evolution Macro-Level
Common Instruction Set Architecture
No need to port
No need for multiple validations
Built in OS integration