LongHaul
Encyclopedia
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.
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.
There are 3 versions of LongHaul:
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
speed throttling and power saving
Power management
Power management is a feature of some electrical appliances, especially copiers, computers 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...
technology developed by VIA Technologies
VIA Technologies
VIA Technologies is a Taiwanese manufacturer of integrated circuits, mainly motherboard chipsets, CPUs, and memory, and is part of the Formosa Plastics Group. It is the world's largest independent manufacturer of motherboard chipsets...
. By executing specialized instructions, software
Computer software
Computer software, or just software, is a collection of computer programs and related data that provide the instructions for telling a computer what to do and how to do it....
can exercise fine control
Control engineering
Control engineering or Control systems engineering is the engineering discipline that applies control theory to design systems with predictable behaviors...
on the bus-to-core frequency ratio
CPU multiplier
In computing, the clock multiplier measures the ratio of an internal CPU clock rate to the externally supplied clock. A CPU with a 10x multiplier will thus see 10 internal cycles for every external clock cycle...
and CPU core voltage
CPU core voltage
The CPU core voltage is the power supply voltage supplied to the CPU , GPU, or other device containing a processing core...
. When the system first boots
Booting
In computing, booting is a process that begins when a user turns on a computer system and prepares the computer to perform its normal operations. On modern computers, this typically involves loading and starting an operating system. The boot sequence is the initial set of operations that the...
, the ratio and voltage are set to hardware defaults
Default (computer science)
A default, in computer science, refers to a setting or value automatically assigned to a software application, computer program or device, outside of user intervention. Such settings are also called presets, especially for electronic devices...
. While the operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
runs, a CPU driver
Device driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
controls the throttling according to how much load
Load (computing)
In UNIX computing, the system load is a measure of the amount of work that a computer system performs. The load average represents the average system load over a period of time...
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
Low-power
In electronics, the term low-power may mean:* Low-power broadcasting, that the power of the broadcast is less, i.e. the radio waves are not intended to travel as far as from typical transmitters....
. However LongHaul is considered similar to Transmeta
Transmeta
Transmeta Corporation was a US-based corporation that licensed low power semiconductor intellectual property. Transmeta originally produced very long instruction word code morphing microprocessors, with a focus on reducing power consumption in electronic devices. It was founded in 1995 by Bob...
's LongRun
LongRun
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...
technology.
There are 3 versions of LongHaul:
- Version 1 only supports dynamic frequency scalingDynamic frequency scalingDynamic frequency scaling is a technique in computer architecture whereby the frequency of a microprocessor can be automatically adjusted "on the fly," either to conserve power or to reduce the amount of heat generated by the chip...
and is implemented in the Cyrix IIICyrix IIICyrix III is an x86-compatible Socket 370 CPU. VIA Technologies launched the processor in February 2000. VIA had recently purchased both Centaur Technology and Cyrix. Cyrix III was to be based upon a core from one of the two companies.- Joshua :...
Samuel (C5A) core and C3VIA C3The 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.-Samuel 2 and Ezra cores:...
Samuel 2 (C5B) stepping 0 core. - Version 2 adds voltage scaling and is implemented in the C3VIA C3The 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.-Samuel 2 and Ezra cores:...
Samuel 2 (C5B) stepping 1-7 and Ezra (C5C) cores. - Version 3 was renamed to PowerSaver and is implemented in the C3VIA C3The 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.-Samuel 2 and Ezra cores:...
Ezra-T (C5N) and Nehemiah cores as well as the C7VIA C7The 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 core. The C7 was officially launched in May 2005,...
Esther (C5J) core. Some variants of the C7-D do not support PowerSaver.
Processors supporting LongHaul
- Cyrix IIICyrix IIICyrix III is an x86-compatible Socket 370 CPU. VIA Technologies launched the processor in February 2000. VIA had recently purchased both Centaur Technology and Cyrix. Cyrix III was to be based upon a core from one of the two companies.- Joshua :...
- some models http://www.cpuscorecard.com/cpuprices/vc3.htm - VIA C3VIA C3The 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.-Samuel 2 and Ezra cores:...
- VIA C7VIA C7The 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 core. The C7 was officially launched in May 2005,...
(PowerSaver) - VIA NanoVIA NanoThe VIA Nano 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...
(PowerSaver)
External links
- VIA C3 in EBGA Datasheet
- Tom's Computer Dictionary - LongHaul entry