Pumping, when referring to

computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...

systems, is an informal term for transmitting a data signal more than one time per

clock signal In electronics and especially synchronous digital circuits, a clock signal (historically also known as ''logic beat'') oscillates between a high and a low state and is used like a metronome to coordinate actions of digital circuits. A clock sign ...

Overview

Early types of system memory (

RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...

), such as

SDRAM Synchronous dynamic random-access memory (synchronous dynamic RAM or SDRAM) is any DRAM where the operation of its external pin interface is coordinated by an externally supplied clock signal. DRAM integrated circuits (ICs) produced from the ...

, transmitted data on only the rising edge of the clock signal. With the advent of ''

double data rate In computing, a computer bus operating with double data rate (DDR) transfers data on both the rising and falling edges of the clock signal. This is also known as double pumped, dual-pumped, and double transition. The term toggle mode is used i ...

synchronous dynamic RAM'' or

DDR SDRAM Double Data Rate Synchronous Dynamic Random-Access Memory (DDR SDRAM) is a double data rate (DDR) synchronous dynamic random-access memory (SDRAM) class of memory integrated circuits used in computers. DDR SDRAM, also retroactively called DDR1 ...

, the data was transmitted on both rising and falling edges. However, quad-pumping has been used for a while for the

front-side bus A front-side bus (FSB) is a computer communication interface (bus) that was often used in Intel-chip-based computers during the 1990s and 2000s. The EV6 bus served the same function for competing AMD CPUs. Both typically carry data between the ...

(FSB) of a computer system. This works by transmitting data at the rising edge, peak, falling edge, and trough of each clock cycle. Intel computer systems (and others) use this technology to reach effective FSB speeds of 1600 MT/s (million transfers per second), even though the FSB clock speed is only 400 MHz (cycles per second). A

phase-locked loop A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal. There are several different types; the simplest is an electronic circuit consisting of a ...

in the CPU then multiplies the FSB clock by a factor in order to get the CPU speed. Example: A

Core 2 Duo Intel Core is a line of streamlined midrange consumer, workstation and enthusiast computer central processing units (CPUs) marketed by Intel, Intel Corporation. These processors displaced the existing mid- to high-end Pentium processors at the ...

E6600 processor is listed as 2.4 GHz with a 1066 MHz FSB. The FSB is known to be quad-pumped, so its clock frequency is 1066/4 = 266 MHz. Therefore, the CPU multiplier is 2400/266, or 9×. The DDR2 RAM that it is compatible with is known to be double-pumped and to have an Input/Output Bus twice that of the true FSB frequency (effectively transferring data 4 times a clock cycle), so to run the system ''synchronously'' (see

) the type of RAM that is appropriate is quadruple 266 MHz, or DDR2-1066 (PC2-8400 or PC2-8500, depending on the manufacturer's labeling.).

References

Computer memory {{Compu-hardware-stub