VIA LongHaul is a CPU speed throttling and power saving technology developed by VIA Technologies. By executing specialized instructions, software can exercise fine control on the bus-to-core frequency ratio and CPU core voltage. When the system first boots, the ratio and voltage are set to hardware defaults. While the operating system runs, a CPU driver controls the throttling according to how much load is put on the CPU.
A central processing unit (CPU), also called a central processor or main processor, is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logic, controlling, and input/output (I/O) operations specified by the instructions. The computer industry has used the term "central processing unit" at least since the early 1960s. Traditionally, the term "CPU" refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.
Power management is a feature of some electrical appliances, especially copiers, computers, GPUs and computer peripherals such as monitors and printers, that turns off the power or switches the system to a low-power state when inactive. In computing this is known as PC power management and is built around a standard called ACPI. This supersedes APM. All recent (consumer) computers have ACPI support.
VIA Technologies Inc., is a Taiwanese manufacturer of integrated circuits, mainly motherboard chipsets, CPUs, and memory. It is the world's largest independent manufacturer of motherboard chipsets. As a fabless semiconductor company, VIA conducts research and development of its chipsets in-house, then subcontracts the actual (silicon) manufacturing to third-party merchant foundries, such as TSMC.
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's LongRun technology.
Low-power electronics are electronics, such as notebook processors, that have been designed to use less electric power.
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.
LongRun and LongRun2 are power management technologies introduced by Transmeta. LongRun was introduced with the Crusoe processor, while LongRun2 was introduced with the Efficeon processor. LongRun2 has since been licensed to Fujitsu, NEC, Sony, Toshiba, and NVIDIA.
There are 3 versions of LongHaul:
- Version 1 only supports dynamic frequency scaling and is implemented in the Cyrix III Samuel (C5A) core and C3 Samuel 2 (C5B) stepping 0 core.
- Version 2 adds voltage scaling 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.
Dynamic frequency scaling is a technique in computer architecture whereby the frequency of a microprocessor can be automatically adjusted "on the fly" depending on the actual needs, to conserve power and reduce the amount of heat generated by the chip. Dynamic frequency scaling helps preserve battery on mobile devices and decrease cooling cost and noise on quiet computing settings, or can be useful as a security measure for overheated systems. Dynamic frequency scaling is used in all ranges of computing systems, ranging from mobile systems to data centers to reduce the power at the times of low workload.
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.
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.
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