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In computing, computer performance is the amount of useful work accomplished by a computer system. Outside of specific contexts, computer performance is estimated in terms of accuracy, efficiency and speed of executing computer program instructions. When it comes to high computer performance, one or more of the following factors might be involved:
The useful work that can be done with any computer depends on many factors besides the processor speed. These factors include the instruction set architecture, the processor's microarchitecture, and the computer system organization (such as the design of the disk storage system and the capabilities and performance of other attached devices), the efficiency of the operating system, and the high ...
For example, an IBM PC with an Intel 80486 CPU running at 50 MHz will be about twice as fast (internally only) as one with the same CPU and memory running at 25 MHz, while the same will not be true for MIPS R4000 running at the same clock rate as the two are different processors that implement different architectures and microarchitectures ...
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 a very approximate guide, the BogoMips can be pre-calculated by the following table. The given rating is typical for that CPU with the then current and applicable Linux version. The index is the ratio of "BogoMips per clock speed" for any CPU to the same for an Intel 386DX CPU, for comparison purposes. [6] [7]
The gap between processor speed and main memory speed has grown exponentially. Until 2001–05, CPU speed, as measured by clock frequency, grew annually by 55%, whereas memory speed only grew by 7%. [1] This problem is known as the memory wall. The motivation for a cache and its hierarchy is to bridge this speed gap and overcome the memory wall.
Some second-level CPU caches run slower than the processor core. When the processor needs to access external memory, it starts placing the address of the requested information on the address bus. It then must wait for the answer, that may come back tens if not hundreds of cycles later. Each of the cycles spent waiting is called a wait state.
Many operating systems, for example Windows, [1] Linux, [2] and macOS [3] will run an idle task, which is a special task loaded by the OS scheduler on a CPU when there is nothing for the CPU to do. The idle task can be hard-coded into the scheduler, or it can be implemented as a separate task with the lowest possible priority.