What is MICROPROCESSORS MICROPROCESSOR

INTRODUCTION OF MICROPROCESSORS

MICROPROCESSOR

Microprocessor is an integrated circuit fabricated on a small piece of silicon and containing several elements of the central processing unit, including the arithmetic-logic and control units and sometimes the floating-point unit. The Computer microprocessors have grown from the inaugural eight-bit units (such as Intel 8088 microprocessors used in the first personal computers) that handled one byte (eight bits), to 16-bit units (Intel 8086 through 80286), to 32-bit systems (Intel 486), to 64-bit units (Intel Pentium).

The term CPU is often used vaguely to include other centrally important parts of a computer such

as caches and input/output controllers, especially in computers with modern microprocessor chips that

include several of these functions in one physical integrated circuit.

Processor Performance Issues

There are several factors that affect the performance of a processor. Among them are availability

of a math coprocessor, clock speed, internal cache memory, and supporting circuitry.

Math Coprocessor

The math coprocessor is used to improve the processor’s number-crunching speed. It does not,

however, increase the speed of simple additions and subtractions. What it does is increase the speed of

calculations that involve floating decimal point operations (such as calculations for algebra and statistics). Since the introduction of the 486, the math coprocessor has been built into the processor. CPU models that preceded the 486 can add a math coprocessor as an option. (There is a special slot for it next to the CPU).

Cache Memory

Cache Memory is a form of SRAM resides on the CPU to quickly access the recently used

information for fast performance of the processor. A typical L1 cache is 256Kb and a typical L2 cache is 1MB.

The L1 cache consists of high speed SRAM on CPU and it stores the most commonly accessed requests hence the data can be accessed at the speed of internal bus, almost full processor speed. When

L1 cache is full and needs to let new data in, the data that has been accessed the least number of times

during the last clock cycle is moved to a new storage area called L2 (Level 2) cache. This also holds SRAM, and it is on the motherboard, although some modern CPUs may have the L2 cache built in. The L2 cache is much larger than the L1 cache, but it operates at a lower speed. If in the preceding clock cycles, theinstruction set is not accessed while in the L2 cache, it is moved out further into the external bus. From here it begins a long, slow journey back to the processor for future use. Quite simply, what were once L2 caches on motherboards now becomes L3 cache when used with microprocessor containing built-in L2 caches.

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