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In computer architecture, cycles per instruction (aka clock cycles per instruction, clocks per instruction, or CPI) is one aspect of a processor's performance: the average number of clock cycles per instruction for a program or program fragment. [1] It is the multiplicative inverse of instructions per cycle.
As each instruction took 20 cycles, it had an instruction rate of 5 kHz. The first commercial PC, the Altair 8800 (by MITS), used an Intel 8080 CPU with a clock rate of 2 MHz (2 million cycles per second). The original IBM PC (c. 1981) had a clock rate of 4.77 MHz (4,772,727 cycles
In computer architecture, instructions per cycle (IPC), commonly called instructions per clock, is one aspect of a processor's performance: the average number of instructions executed for each clock cycle. It is the multiplicative inverse of cycles per instruction. [1] [2] [3]
Before standard benchmarks were available, average speed rating of computers was based on calculations for a mix of instructions with the results given in kilo instructions per second (kIPS). The most famous was the Gibson Mix , [ 2 ] produced by Jack Clark Gibson of IBM for scientific applications in 1959.
The most characteristic aspect of RISC is executing at least one instruction per cycle. [31] Single-cycle operation is described as "the rapid execution of simple functions that dominate a computer's instruction stream", thus seeking to deliver an average throughput approaching one instruction per cycle for any single instruction stream. [45]
Another unit of throughput is instructions per cycle (IPC) and its reciprocal, cycles per instruction (CPI), is another unit of latency. Speedup is dimensionless and defined differently for each type of quantity so that it is a consistent metric.
If this instruction is ignored, there is a one cycle per taken branch IPC penalty, which is adequately large. There are four schemes to solve this performance problem with branches: Predict Not Taken: Always fetch the instruction after the branch from the instruction cache, but only execute it if the branch is not taken.
Cycle i + 1: an instruction from thread B is issued. Cycle i + 2: an instruction from thread C is issued. This type of multithreading was first called barrel processing, in which the staves of a barrel represent the pipeline stages and their executing threads. Interleaved, preemptive, fine-grained or time-sliced multithreading are more modern ...