Unformatted text preview: performs some simple computational task such as adding two numbers, reading data from memory, or writing data to memory. For machines with complex instructions, such as an IA32 processor, an instruction can be decoded into a variable number of operations. The details vary from one processor design to another, but we attempt to describe a typical implementation. In this machine, decoding the instruction
addl %eax,%edx yields a single addition operation, whereas decoding the instruction
addl %eax,4(%edx) yields three operations: one to load a value from memory into the processor, one to add the loaded value to the value in register %eax, and one to store the result back to memory. This decoding splits instructions to allow a division of labor among a set of dedicated hardware units. These units can then execute the different parts of multiple instructions in parallel. For machines with simple instructions, the operations correspond more closely to the original instructions. The EU receives operations f...
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