CMOS.

Complementary metal oxide semiconductor. CMOS is the semiconductor technology that is currently used for manufacturing processors and memories. While other technologies (silicon-germanium and gallium-arsenide) can support higher clock rates, their higher cost and lower integration levels have precluded their successful use in supercomputers.

commodity processor.

A processor that is designed for a broad market and manufactured in large numbers, in contrast to a custom processor.

commodity supercomputer.

A supercomputer built from commodity parts.

communication.

The movement of data from one part of a system to another. Local communication is the movement of data between the processor and memory; global communication is the movement of data from one node to another.

composite theoretical performance.

CTP is a measure of the performance of a computer that is calculated using a formula that combines various system parameters. CTP is commonly measured in millions of theoretical operations per second (MTOPS). Systems with a CTP above a threshold (currently 190,000 MTOPS) are subject to stricter export controls. The threshold is periodically raised. While CTP is relatively easy to compute, it bears limited relationship to actual performance.

computational fluid dynamics (CFD).

The simulation of flows, such as the flow of air around a moving car or plane.

computational grid.

Originally used to denote a hardware and software infrastructure that enables applying the resources of many computers to a single problem. Now increasingly used to denote more broadly a hardware and software infrastructure that enables coordinated resource sharing within dynamic organizations consisting of individuals, institutions, and resources.

control parallelism.

Parallelism that is achieved by the simultaneous execution of multiple threads.

cost/performance ratio.

The ratio between the cost of a system and the effective performance of the system. This ratio is sometimes estimated by the ratio between the purchase cost of a computer and the performance of the computer as measured by a benchmark. A more accurate but hard to estimate measure is the ratio between the total cost of ownership of a platform and the value contributed by the platform.

COTS.

Commercial, off-the-shelf.

CPU.

Central processing unit, the core unit of a computer that fetches instructions and data and executes the instructions. Often used as a synonym for processor.