In computing, a double pumped computer bus transfers data on both the rising and falling edges of the clock signal, effectively doubling the data transmission rate without having to deal with the additional problems of timing skew that increasing the number of data lines would introduce. This is also known as dual-pumped, double data rate, and double transition. Originally, the word computing was synonymous with counting and calculating* Computational models DBLP, as of February 2005, now lists over 600 000 bibliographic entries on computer science and several thousand links to the home pages of computer scientists Hardware See information processor for a high-level block diagram. ... In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers. ... In synchronous digital electronics, such as most computers, a clock signal is a signal used to coordinate the actions of two or more circuits. ... Timing skew is a problem that can occur on many kinds of computer bus. ...

This technique has been used for the front side bus, Ultra-3 SCSI, the AGP bus and DDR SDRAM, amongst others. Front Side Bus (FSB) is the term used to describe the CPU data bus. ... SCSI stands for Small Computer System Interface, and is a standard interface for transferring data between devices on a computer bus. ... The Accelerated Graphics Port (also called Advanced Graphics Port) is a high-speed point-to-point channel for attaching a single device (generally a graphics card) to a computers motherboard, primarily to assist in the acceleration of 3D computer graphics. ... DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. ...

For some applications, even double pumping has proven insufficient and quad pumping has been used; transferring data four times per clock. Intel's Pentium 4 utilizes this technique to achieve an 800MHz (200x4) FSB, or more recently 1066MHz (266x4). Also, some say that the HyperTransport bus on newer AMD Socket 754 and 939 chips is double-pumped. Others claim that the bus cannot attain its full speed due to motherboard limitations, however, the generally accepted version is that the bus is double data rate and thus the 1000MHz bus becomes a 2000MHz bus on a Socket 939 motherboard. Socket 754, by specification (http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/31410.pdf) runs at a slower 800MHz, or 1600MHz. Intel Corporation (NASDAQ: INTC) (founded 1968) is a US-based multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... Pentium 4 (with hyper-threading) brand logo The Pentium 4 is a seventh-generation x86 architecture microprocessor produced by Intel and is their first all-new CPU design since the Pentium Pro of 1995. ... FSB may stand for one of the following. ... Advanced Micro Devices, Inc. ...

An alternative to double or quad pumping is to make the link self-clocking. This tactic was chosen by Infiniband and PCI Express. InfiniBand is a high-speed serial computer bus, intended for both internal and external connections. ... PCI Express (formerly known as 3GIO for 3rd Generation I/O, not to be mistaken with PCI-X) is an implementation of the PCI computer bus that uses existing PCI programming concepts and communications standards, but bases it on a much faster serial communications system. ...

It is often difficult to know how to refer to the speed of a double-pumped bus. Some people talk about the speed of the clock signal and some people prefer to refer to the number of transfers per second. It is less ambiguous to discuss the raw bandwidth of a bus as this also takes into account the width of the bus: thus DDR SDRAM that runs on a clock of 100MHz, with data transfer at 200MHz, is called DDR200 and PC1600, referring to the bandwidth. However, this does not take into account the bus protocol overhead or latencies, both of which can reduce the effective bandwidth of a bus to a fraction of the raw bandwidth.