Macroarchitecture vs microarchitecture
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PipeliningParallelism is achieved by starting to execute one instruction before the previous one is finished. • The simplest kind overlaps the execution of one instruction with the fetch of the next instruction, as on a RISC. Because two instructions can be processed simultaneously, we say that the pipeline has two stages. 
Load and store reference memory, so they take two cycles. • A pipeline may have more than two stages. Suppose, for example, that an instruction consists of four phases: 1. Instruction fetch 3. Operand fetch 2. Instruction decode 4. Execute In a non-pipelined processor, these must be executed sequentially, so that a result is only available each four pipeline cycles (subcycles): In a pipelined processor, after a delay to load the pipeline, a result is available each pipeline cycle. 
• The type of pipelining described above achieves instruction-level parallelism—execution of multiple instructions in parallel. • It is also possible to use pipelining to achieve data parallelism. A vector processor usually has a long pipeline, and allows a large number of the same operations to take place concurrently. (Same operations, different data = • A single “processor” may possess multiple pipelines, allowing different operations to use different pipelines (e.g., there might be a specialized addition pipeline, and another load pipeline). For example, the CDC 6600 had ten separate functional units, with a scoreboard to keep track of which was in use at any time. 
• Branches are a problem for pipelined computers. Execution of some instructions may take longer than others. If there are two (or more) units capable of performing a given function (e.g., multiplication), then two operations of that type may be performed at once, providing that— Lecture 1 Architecture of Parallel Computers Directory: efg -> 506 506 -> Simulating ocean currents efg -> European Computer and Video Game Archives and Museums Joining Forces to Preserve Gaming Legacy Download 132.66 Kb. Share with your friends:
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