|This article needs additional citations for verification. (September 2014)|
In computing, hardware acceleration is the use of computer hardware to perform some functions faster than is possible in software running on a more general-purpose CPU. Examples of hardware acceleration include blitting acceleration functionality in graphics processing units (GPUs) and regular expression hardware acceleration for spam control in the server industry.
Normally, processors are sequential, and instructions are executed one by one. Various techniques are used to improve performance; hardware acceleration is one of them. The main difference between hardware and software is concurrency, allowing hardware to be much faster than software. Hardware accelerators are designed for computationally intensive software code. Depending upon granularity, hardware acceleration can vary from a small functional unit to a large functional block (like motion estimation in MPEG-2).
The hardware that performs the acceleration, when in a separate unit from the CPU, is referred to as a hardware accelerator, or often more specifically as a 3D accelerator, cryptographic accelerator, etc. Those terms, however, are older and have been replaced with less descriptive terms like video card or network adapter.
In the hierarchy of general-purpose processors such as CPUs, more specialized processors such as GPUs, fixed-function implemented on FPGAs, and fixed-function implemented on ASICs; there is a tradeoff between flexibility and efficiency, with efficiency increasing by orders of magnitude when any given application is implemented higher up that hierarchy. 
- DirectX Video Acceleration (DXVA)
- Digital signal processor
- Field-programmable gate array
- SSL acceleration
- TCP Offload Engine