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Instruction processing style. Specifies the number of “operands” an instruction “operates” on and how it does so. 0, 1, 2, 3 address machines: 0-address: stack machine (push A, pop A, op) 1-address: accumulator machine (ld A, st A, op A) 2-address: 2-operand machine (one is both source and dest)
1 Introduction Instruction Set Architecture –the portion of the machine visible to the assembly level programmer or to the compiler writer –To use the hardware of a computer, we must speakits language –The words of a computer language are called instructions, and its vocabulary is called an instruction set instruction set software hardware
Computers with different microarchitecture can share the same instruction set. For example, the Intel Pentium and AMD Athlon processors implement nearly identical versions of the Intel x86 instruction set, but if the terms of its internal design, the difference is radical.
Variable-length instructions (x86, VAX) require multi-step fetch and decode, but allow for a much more flexible and compact instruction set. – Low on memory usage, since many simple instructions only use one or two bytes. – Hard to decode. The decoder needs to first determine the length of next instruction in the memory before decoding it.
26 lut 2020 · Architecture: (also ISA or instruction set architecture). The parts of a processor design one needs in order to understand or write assembly/machine code. Examples: instruction set specification, registers. Microarchitecture: implementation of the architecture. Examples: cache sizes and core frequency.
What Makes a Good ISA? ¥Programmability. ¥Easy to express programs efficiently? ¥Implementability. ¥Easy to design high-performane implementations? ¥More recently ¥Easy to design low-power implementans? ¥Easy to design high-reliability impleentations? ¥Easy to design low-costimplementatns?
Architecture: defines what a computer system does in response to a program and a set of data. Programmer visible elements of computer system. Implementation: defines how a computer does it. Sequence of steps to complete operations. Time to execute each operation. Hidden “bookkeeping” functions.
