Chapter 22Instructions:•Language of the Machine•Stored program concept: data + instructions in numbers•We’ll be working with the MIPS instruction set architecture–similar to other architectures developed since the 1980's–Almost 100 million MIPS processors manufactured in 2002–used by NEC, Nintendo, Cisco, Silicon Graphics, Sony, …RISC - Reduced Instruction Set Computer• RISC philosophy• fixed instruction lengths• load-store instruction sets• limited addressing modes• limited operations• MIPS, Sun SPARC, HP PA-RISC, IBM PowerPC, Intel (Compaq) Alpha, …• Instruction sets are measured by how well compilers use them as opposed to how well assembly language programmers use themDesign goals: speed, cost , size, power consumption, reliability, memory space4MIPS arithmetic•All instructions have 3 operands•Operand order is fixed (destination first)!Example:! C code: ! a = b + c! MIPS ‘code’:! add a, b, c ! ! ! !! ! ! (we’ll talk about registers in a bit)compilation“The natural number of operands for an operation like addition is three…requiring every instruction to have exactly three operands, no more and no less, conforms to the philosophy of keeping the hardware simple”For a given level of function, however, that system is best in which one can specify things with the most simplicity and straightforwardness. … Simplicity and straightforwardness proceed from conceptual integrity. … Ease of use, then, dictates unity of design, conceptual integrity. The Mythical Man-Month, Brooks, pg 44MIPS Arithmetic Instructions• MIPS assembly language arithmetic statementadd $t0, $s1, $s2sub $t0, $s1, $s2•Each arithmetic instruction performs only one operation•Each arithmetic instruction fits in 32 bits and specifies exactly three operands•Those operands are all contained in the datapath’s registers ($t0,$s1,$s2) – indicated by $•only 32 registers provided•Operand order is fixed (destination first)•Each register contains 32 bits (a word)•Design Principle: smaller is faster.