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Unformatted text preview: IZING PROGRAM PERFORMANCE order in which instructions execute need not correspond to their ordering in the assembly program. The overall design has two main parts. The Instruction Control Unit (ICU) is responsible for reading a sequence of instructions from memory and generating from these a set of primitive operations to perform on program data. The Execution Unit (EU) then executes these operations. The ICU reads the instructions from an instruction cache—a special, high-speed memory containing the most recently accessed instructions. In general, the ICU fetches well ahead of the currently executing instructions, so that it has enough time to decode these and send operations down to the EU. One problem, however, is that when a program hits a branch,1 there are two possible directions the program might go. The branch can be taken, with control passing to the branch target. Alternatively, the branch can be not taken, with control passing to the next instruction in the instruction sequence. Modern processors employ a technique known as branch prediction, where they guess whether or not a...
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This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.

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