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Microprocessor Performance Factors
4. A microprocessor’s performance is affected by several factors, including clock speed, word size, cache size, instruction set, and processing techniques.
5. The microprocessor clock is a timing device that sets the pace for executing instructions. The speed of a microprocessor is usually specified in megahertz (MHz) or gigahertz. A cycle is the smallest unit of time in a microprocessor’s universe. Every action a processor performsis measured by these cycles. The clock speed is not equal to the number of instructions a processor can execute in one second. In many computers, some instructions occur within one cycle, but other instructions might requiremultiple cycles. Some processors can execute several instructions in a single clock cycle.
6. Word size refers to the number of bits that a microprocessor can manipulate at one time. Word size is based on the size of registers in the ALU and the capacity of circuits that lead to those registers. A processor with a 32-bit word size, for example, has 32-bit registers, processes 32 bits at a time, and is referred to as a “32-bit processor”. Processors with a larger word size can process more data during each processor cycle that leads to increased computer performance.
7. Cache or “RAM cache” or “cache memory” is special high-speed memory that allows a microprocessor to access data more rapidly than from memory located elsewhere on the system board. Cache capacity is usually measured in kilobytes.
8. As chip designers developed various instruction sets for microprocessors, they tendedto add increasingly complex instructions, each requiring several clock cycles for execution. A microprocessor with such an instruction set uses CISC (complex instruction set computer) technology. A microprocessor with a limited set of simple instructions uses RISC (reduced instruction set computer) technology. A RISC processor performs most instructions faster than a CISC processor. It might, however, require more of these simple instructions to complete a task than a CISC processor requires for the same task. Most processors in today’s personal computer use CISC technology.
9. Some processors execute instruction “serially” – that is, one instruction at a time. With serial processing, the processor must complete all steps in the instruction cycle before it begins to execute the next instruction. However, using a technology called pipelining, a processor can begin executing an instruction before it completes the previous instruction. Many of today’s microprocessors also perform parallel processing, in which multiple instructions are executed at the same time. Pipelining and parallel processing enhance processorperformance.
10. Some computers have a single chip containingthe circuitry for two microprocessors. A dual core processor is faster than one with a single core.
11. Various testing laboratories run a series of tests to gauge the overall speed of a microprocessor. The results of these tests – called benchmarks – can then be comparedto the results for other microprocessors.
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