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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 ...
Thus, a representation that compresses the storage size of a file from 10 MB to 2 MB yields a space saving of 1 - 2/10 = 0.8, often notated as a percentage, 80%. For signals of indefinite size, such as streaming audio and video, the compression ratio is defined in terms of uncompressed and compressed data rates instead of data sizes:
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.
1×10 −1: multiplication of two 10-digit numbers by a 1940s electromechanical desk calculator [1] 3×10 −1: multiplication on Zuse Z3 and Z4, first programmable digital computers, 1941 and 1945 respectively; 5×10 −1: computing power of the average human mental calculation [clarification needed] for multiplication using pen and paper
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.
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.
The quality the codec can achieve is heavily based on the compression format the codec uses. A codec is not a format, and there may be multiple codecs that implement the same compression specification – for example, MPEG-1 codecs typically do not achieve quality/size ratio comparable to codecs that implement the more modern H.264 specification.