12 THE x86 MICROPROCESSORS
0.4 | RISC and CISC Architectures
Two terms that are likely to be encountered frequently while reading about computer architecture
are RISC and CISC. RISC stands for Reduced Instruction Set Computer and CISC means
Complex Instruction Set Computer. Since a lot of controversy surrounds these two terms, let us
try to fi nd out what it is all about.
In the early days of microprocessor development, the trend was to have complex instruc-
tions implemented fully using hardware. For example, the multiply instruction is a complex
instruction which needs a dedicated hardware multiplier. Because hardware is fast, execution is
fast, but with lots of such complex instructions, the hardware budget is naturally high. is is
the ...