Coprocessor

Others are independent processors in their own right, capable of working asynchronously; they are still not optimized for general-purpose code, or they are incapable of it due to a limited instruction set focused on accelerating specific tasks.

It is common for these to be driven by direct memory access (DMA), with the host processor (a CPU) building a command list.

The PlayStation 2's Emotion Engine contained an unusual DSP-like SIMD vector unit capable of both modes of operation.

To make the best use of mainframe computer processor time, input/output tasks were delegated to separate systems called Channel I/O.

Math coprocessors were popular purchases for users of computer-aided design (CAD) software and scientific and engineering calculations.

The Amiga custom chipset includes such a unit known as the Copper, as well as a blitter for accelerating bitmap manipulation in memory.

Users that only used the PC for word processing, for example, saved the high cost of the coprocessor, which would not have accelerated performance of text manipulation operations.

It used the same programming technique as 8087 for input/output operations, such as transfer of data from memory to a peripheral device, and so reducing the load on the CPU.

The Intel 80386 microprocessor used an optional "math" coprocessor (the 80387) to perform floating-point operations directly in hardware.

[2] The Motorola 68000 family had the 68881/68882 coprocessors which provided similar floating-point speed acceleration as for the Intel processors.

In 2008, Khronos Group released the OpenCL with the aim to support general-purpose CPUs, ATI/AMD and Nvidia GPUs (and other accelerators) with a single common language for compute kernels.

Nonetheless, specialized units remain popular away from desktop machines, and for additional power, and allow continued evolution independently of the main processor product lines.