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In 2002, an Intel Pentium 4 model was introduced as the first CPU with a clock rate of 3 GHz (three billion cycles per second corresponding to ~ 0.33 nanoseconds per cycle). Since then, the clock rate of production processors has increased more slowly, with performance improvements coming from other design changes.
For example, with two executions units, two new instructions are fetched every clock cycle by exploiting instruction-level parallelism, therefore two different instructions would complete stage 5 in every clock cycle and on average the number of clock cycles it takes to execute an instruction is 1/2 (CPI = 1/2 < 1).
The final result comes from dividing the number of instructions by the number of CPU clock cycles. The number of instructions per second and floating point operations per second for a processor can be derived by multiplying the number of instructions per cycle with the clock rate (cycles per second given in Hertz) of the processor in question ...
CPU instruction rates are different from clock frequencies, usually reported in Hz, as each instruction may require several clock cycles to complete or the processor may be capable of executing multiple independent instructions simultaneously.
For example, DDR3-2000 memory has a 1000 MHz clock frequency, which yields a 1 ns clock cycle. With this 1 ns clock, a CAS latency of 7 gives an absolute CAS latency of 7 ns. Faster DDR3-2666 memory (with a 1333 MHz clock, or 0.75 ns exactly; the 1333 is rounded) may have a larger CAS latency of 9, but at a clock frequency of 1333 MHz the ...
Pipelining typically reduces the processor's cycle time and increases the throughput of instructions. The speed advantage is diminished to the extent that execution encounters hazards that require execution to slow below its ideal rate. A non-pipelined processor executes only a single instruction at a time.
In computing, the clock multiplier (or CPU multiplier or bus/core ratio) sets the ratio of an internal CPU clock rate to the externally supplied clock. This may be implemented with phase-locked loop (PLL) frequency multiplier circuitry. A CPU with a 10x multiplier will thus see 10 internal cycles for every external clock cycle. For example, a ...
It therefore allows more throughput (the number of instructions that can be executed in a unit of time which can even be less than 1) than would otherwise be possible at a given clock rate. Each execution unit is not a separate processor (or a core if the processor is a multi-core processor ), but an execution resource within a single CPU such ...