Basic structure of a Pentium microprocessor

A Pentium processor’s major functional components are: Core: The heart of a Pentium is the execution unit. The Pentium has two parallel integer pipelines enabling it to read, interpret, execute and despatch two instructions simultaneously. Branch Predictor: The branch prediction unit tries to guess which sequence will be executed each time the program contains a conditional jump, so that the Prefetch and Decode Unit can get the instructions ready in advance. Floating Point Unit: The third execution unit in a Pentium, where non-integer calculations are performed. Level 1 Cache: The Pentium has two on-chip caches of 8KB each, one for code and one for data, which are far quicker than the larger external secondary cache. Bus Interface: This brings a mixture of code and data into the CPU, separates the two ready for use, and then recombines them and sends them back out. All the elements of the processor stay in step by use of a clock which dictates how fast it operates. The very first microprocessor had a 100KHz clock, whereas the Pentium Pro uses a 200MHz clock, which is to say it ticks 200 million times per second. As the clock ticks, various things happen. The Program Counter (PC) is an internal memory location which contains the address of the next instruction to be executed. When the time comes for it to be executed, the Control Unit transfers the instruction from memory into its Instruction Register (IR). At the same time, the PC is incremented so that it points to the next instruction in sequence; now the processor executes the instruction in the IR. Some instructions are...

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