VIA LongHaul is a CPU speed throttling and power saving technology developed by

VIA Technologies VIA Technologies Inc. (), is a Taiwanese manufacturer of integrated circuits, mainly motherboard chipsets, CPUs, and memory. It was the world's largest independent manufacturer of motherboard chipsets. As a fabless semiconductor company, VIA ...

. By executing specialized instructions,

software Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work. ...

can exercise fine

control Control may refer to: Basic meanings Economics and business * Control (management), an element of management * Control, an element of management accounting * Comptroller (or controller), a senior financial officer in an organization * Controllin ...

on the bus-to-core frequency ratio and CPU core voltage. When the system first

boots A boot is a type of footwear. Boot or Boots may also refer to: Businesses * Boot Inn, Chester, Cheshire, England * Boots (company), a high-street pharmacy chain and manufacturer of pharmaceuticals in the United Kingdom * The Boot, Cromer St ...

, the ratio and voltage are set to hardware defaults. While the

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...

runs, a ''CPU driver'' controls the throttling according to how much load is put on the CPU. This fine control over the CPU's operating parameters brings LongHaul in contrast to other competing technologies, where a CPU is typically allowed to switch between only two states - one that is fast but power-consuming and one that is slow but uses less power. However LongHaul is considered similar to

Transmeta Transmeta Corporation was an American fabless semiconductor company based in Santa Clara, California. It developed low power x86 compatible microprocessors based on a VLIW core and a software layer called Code Morphing Software. Code Morphing ...

's LongRun technology. There are 3 versions of LongHaul: * Version 1 only supports

dynamic frequency scaling Dynamic frequency scaling (also known as CPU throttling) is a power management technique in computer architecture whereby the frequency of a microprocessor can be automatically adjusted "on the fly" depending on the actual needs, to conserve ...

and is implemented in the

Cyrix III Cyrix III is an x86-compatible Socket 370 CPU. VIA Technologies launched the processor in February 2000. VIA had purchased both Centaur Technology and Cyrix. Cyrix III was to be based upon a core from one of the two companies. History The Cy ...

Samuel (C5A) core and C3 Samuel 2 (C5B) stepping 0 core. * Version 2 adds

voltage scaling Dynamic voltage scaling is a power management technique in computer architecture, where the voltage used in a component is increased or decreased, depending upon circumstances. Dynamic voltage scaling to increase voltage is known as overvolting; d ...

and is implemented in the C3 Samuel 2 (C5B) stepping 1-7 and Ezra (C5C) cores. * Version 3 was renamed to PowerSaver and is implemented in the C3 Ezra-T (C5N) and Nehemiah cores as well as the C7 Esther (C5J) core. Some variants of the C7-D do not support PowerSaver.

Processors supporting LongHaul

- some model

*

VIA C3 The VIA C3 is a family of x86 central processing units for personal computers designed by Centaur Technology and sold by VIA Technologies. The different CPU cores are built following the design methodology of Centaur Technology. In addition to ...

VIA C7 The VIA C7 is an x86 central processing unit designed by Centaur Technology and sold by VIA Technologies. Product history The C7 delivers a number of improvements to the older VIA C3 cores but is nearly identical to the latest VIA C3 Nehemiah ...

(PowerSaver) *

VIA Nano The VIA Nano (formerly code-named VIA Isaiah) is a 64-bit CPU for personal computers. The VIA Nano was released by VIA Technologies in 2008 after five years of development by its CPU division, Centaur Technology. This new Isaiah 64-bit architec ...

(PowerSaver)

External links

VIA C3 in EBGA Datasheet
- ''LongHaul'' entry Computer hardware tuning Clock signal VIA Technologies {{Compu-hardware-stub