Computer Performance - Technical Performance Metrics

Technical Performance Metrics

There are a wide variety of technical performance metrics that indirectly affect overall computer performance.

Because there are too many programs to test a CPU's speed on all of them, benchmarks were developed. The most famous benchmarks are the SPECint and SPECfp benchmarks developed by Standard Performance Evaluation Corporation and the ConsumerMark benchmark developed by the Embedded Microprocessor Benchmark Consortium EEMBC.

Some important measurements include:

• Instructions per second – Most consumers pick a computer architecture (normally Intel IA32 architecture) to be able to run a large base of pre-existing, pre-compiled software. Being relatively uninformed on computer benchmarks, some of them pick a particular CPU based on operating frequency (see megahertz myth).
• FLOPS – The number of floating-point operations per second is often important in selecting computers for scientific computations.
• Performance per watt – System designers building parallel computers, such as Google, pick CPUs based on their speed per watt of power, because the cost of powering the CPU outweighs the cost of the CPU itself.
• Some system designers building parallel computers pick CPUs based on the speed per dollar.
• System designers building real-time computing systems want to guarantee worst-case response. That is easier to do when the CPU has low interrupt latency and when it has deterministic response. (DSP)
• Computer programmers who program directly in assembly language want a CPU to support a full-featured instruction set.
• Low power – For systems with limited power sources (e.g. solar, batteries, human power).
• Small size or low weight - for portable embedded systems, systems for spacecraft.
• Environmental impact – Minimizing environmental impact of computers during manufacturing and recycling as well as during use. Reducing waste, reducing hazardous materials. (see Green computing).
• Giga-updates per second - a measure of how frequently the RAM can be updated

Occasionally a CPU designer can find a way to make a CPU with better overall performance by improving one of these technical performance metrics without sacrificing any other (relevant) technical performance metric—for example, building the CPU out of better, faster transistors. However, sometimes pushing one technical performance metric to an extreme leads to a CPU with worse overall performance, because other important technical performance metrics were sacrificed to get one impressive-looking number—for example, the megahertz myth.