Outline Architecture of a RISC Processor Implementation Pirouz

Outline Architecture of a RISC Processor Implementation Pirouz Bazargan Sabet December 2003

Implementation RISC vs. CISC concept Concept of pipeline An implementation of Mips Pipeline’s problems Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept A given architecture can be implemented in many different ways performance complexity implementation Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept The RISC concept has been developped in early 80’s CISC RISC Complex Instruction Set Computer Reduce Instruction Set Computer Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept The basic idea of CISCs Use the constante improvement of the technology to offer a more powerful architecture It is easier to program with a powerful assembly language Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept high level languages instruction set Reduce the “semantic gap” between high level languages and the assembly language hardware Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept Examples: Strcmp (IBM 370) : string compare Add with 3 operands in memory (VAX) Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept The basic idea of RISCs Simplify the hardware It is easier to design a simple hardware Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept 3 factors have worked towards the apparition of the RISC concept Economical factor User factor Technology factor Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept Economical factor A=B+C; VAX complex instruction Add @a, @b, @c Pirouz Bazargan Sabet Equivalent Mips code Lw Lw Add Sw R 1, @b R 2, @c R 3, R 1, R 2 R 3, @a December 2003

RISC vs. CISC concept Economical factor A given program compiled for a RISC processor is 2 to 3 times bigger than the same code generated for a CISC Strong argument in favor of CISC …… in 60’s - 70’s Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept User factor It is easier to program with a powerful assembly language Strong argument in favor of CISC Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept User factor design a new processeur a check the MIX prog add 8% compiler bne 6% assembly code Pirouz Bazargan Sabet complex 0. 0% December 2003

RISC vs. CISC concept User factor complex instructions are NOT used in contradiction with the CISC concept Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept User factor In 80’s assembly language programmers have been replaced by compilers A compiler can only use simple instructions Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept User factor It is easier to program with a powerful assembly language ……. for a human Strong argument in favor of CISC …… in 60’s - 70’s Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept Technology factor Moore’s law Time-to-market Pirouz Bazargan Sabet # of trans. frequency Risk of fail December 2003

RISC vs. CISC concept Technology factor Complex architecture (CISC) Complex design Longer time-to-market (3 -4 years) Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept Technology factor Simple architecture (RISC) Simplementation Short time project Better prevision Lower risk Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept RISC concept simplify the hardware gain in speed gain in time-to-market The gap between high level languages and the assembly language can be filled by the compiler Pirouz Bazargan Sabet December 2003

RISC vs. CISC concept Reduce Instruction Set Computer Pirouz Bazargan Sabet Reject Important Stuffs into the Compiler December 2003