Instructions Words of the Machine's language More primitive than higher level languages e.g., no sophisticated control flow ° Very restrictive e.g., MIPS Arithmetic Instructions We will be working with the mips instruction set architecture similar to other architectures developed since the 1980s used by NEc, Nintendo, Silicon Graphics, Sony Design goals: maximize performance and minimize cost, reduce design time 北京大学计算机科学技术系 计算机系统结枃教硏室
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MIPS arithmetic All instructions have 3 operands Operand order is fixed ( destination first Example: c code A =B+C MIPS code: add Ss0, Ssl, $s2 associated with variables by compiler) 北京大学计算机科学技术系 计算机系统结枃教硏室
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MIPS arithmetic Design Principle: simplicity favors regularity. Why? of course this complicates some things c code: A=b+C+d: EE F-A MIPS code: add sto, ss1, ss2 add sso, sto, $s3 sub ss4, Ss5, Ss0 Operands must be registers, only 32 registers provided Design Principle: smaller is faster. Why? 北京大学计算机科学技术系 计算机系统结枃教硏室
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Registers vs Memory Arithmetic instructions operands must be registers, only 32 registers provided Compiler associates variables with registers What about programs with lots of variables Control Input Memory Datapath Output Processor vO 北京大学计算机科学技术系 计算机系统结枃教硏室
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Memory Organization viewed as a large, single-dimension array, with an address A memory address is an index into the array Byte addressing"means that the index points to a byte of memory 0「8 B bits of data 1「8 8 bits of data 2 8 bits of data 8 bits of data 4「8 B bits of data 8 bits of data 6「8 bits of data 北京大学计算机科学技术系 计算机系统结枃教硏室
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