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For example, with six executions units, six new instructions are fetched in stage 1 only after the six previous instructions finish at stage 5, therefore on average the number of clock cycles it takes to execute an instruction is 5/6 (CPI = 5/6 < 1). To get better CPI values with pipelining, there must be at least two execution units.
Generally speaking, however, complex instructions inflate the number of clock cycles per instruction because they must be decoded into simpler micro-operations actually performed by the hardware. After converting X86 binary to the micro-operations used internally, the total number of operations is close to what is produced for a comparable RISC ...
The number of instructions per second is an approximate indicator of the likely performance of the processor. The number of instructions executed per clock is not a constant for a given processor; it depends on how the particular software being run interacts with the processor, and indeed the entire machine, particularly the memory hierarchy.
We can also measure speedup in cycles per instruction (CPI) which is a latency. First, we execute the program with the standard branch predictor, which yields a CPI of 3. Next, we execute the program with our modified branch predictor, which yields a CPI of 2.
These cache hits and misses contribute to the term average access time (AAT) also known as AMAT (average memory access time), which, as the name suggests, is the average time it takes to access the memory. This is one major metric for cache performance measurement, because this number becomes highly significant and critical as processor speed ...
A superscalar processor usually sustains an execution rate in excess of one instruction per machine cycle. But merely processing multiple instructions concurrently does not make an architecture superscalar, since pipelined, multiprocessor or multi-core architectures also achieve that, but with different methods.
A CPI is a statistical estimate constructed using the prices of a sample of representative items whose prices are collected periodically. Sub-indices and sub-sub-indices can be computed for different categories and sub-categories of goods and services, which are combined to produce the overall index with weights reflecting their shares in the total of the consumer expenditures covered by the ...
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