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In computing, double pumped (also known as dual-pumped, double data rate and double transition) refers to a computer bus design that 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 clock skew.

This technique has been used for the Front side bus, Ultra-3 SCSI, the AGP bus and DDR SDRAM, amongst others.

For some applications, even double pumping has proven insufficient and quad pumping has been used; transferring data four times per clock. One example of this is DDR-II RAM.

An alternative to double or quad pumping is to make the link self-clocking. This tactic was chosen by Infiniband and PCI-Express.

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. It 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.

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Topics: Double Pumped, Double Jeopardy, Double Stops, Double barreled...

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