Quad Data Rate
Encyclopedia
Quad data rate is a communication signaling technique wherein data are transmitted at four points in the clock cycle: on the rising and falling edges, and at two intermediate points between them. The intermediate points are defined by a 2nd clock that is 90° out of phase
Phase (waves)
Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...

 from the first. The effect is to deliver four bits of data per signal line per clock cycle.

In a quad data rate system, the data lines operate at twice the frequency of the clock signal. This is in contrast to double data rate
Double data rate
In computing, a computer bus operating with double data rate 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....

 systems where the clock and data lines operate at the same frequency.

QDR technology was introduced by Intel in their Willamette core Pentium 4
Pentium 4
Pentium 4 was a line of single-core desktop and laptop central processing units , introduced by Intel on November 20, 2000 and shipped through August 8, 2008. They had a 7th-generation x86 microarchitecture, called NetBurst, which was the company's first all-new design since the introduction of the...

 CPU
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...

, and is currently employed in their Atom
Intel Atom
Intel Atom is the brand name for a line of ultra-low-voltage x86 and x86-64 CPUs from Intel, designed in 45 nm CMOS and used mainly in netbooks, nettops, embedded application ranging from health care to advanced robotics and Mobile Internet devices...

, Pentium 4
Pentium 4
Pentium 4 was a line of single-core desktop and laptop central processing units , introduced by Intel on November 20, 2000 and shipped through August 8, 2008. They had a 7th-generation x86 microarchitecture, called NetBurst, which was the company's first all-new design since the introduction of the...

, Celeron
Celeron
Celeron is a brand name given by Intel Corp. to a number of different x86 computer microprocessor models targeted at budget personal computers....

, Pentium D
Pentium D
The Pentium D brand refers to two series of desktop dual-core 64-bit x86-64 microprocessors with the NetBurst microarchitecture manufactured by Intel. Each CPU comprised two dies, each containing a single core, residing next to each other on a multi-chip module package. The brand's first processor,...

, and Core 2 Processor
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...

 ranges. This technology has allowed Intel to produce chipsets and microprocessors that can communicate with each other at data rates expected of the traditional FSB
Front side bus
A front-side bus is a computer communication interface often used in computers during the 1990s and 2000s.It typically carries data between the central processing unit and a memory controller hub, known as the northbridge....

 technology running from 400 MT
Megatransfer
In computer technology, transfers per second and its more common derivatives gigatransfers per second and megatransfers per second are informal language that refer to the number of operations transferring data that occur in each second in some given data-transfer channel. It is also known as...

/s to 1600 MT
Megatransfer
In computer technology, transfers per second and its more common derivatives gigatransfers per second and megatransfers per second are informal language that refer to the number of operations transferring data that occur in each second in some given data-transfer channel. It is also known as...

/s, while maintaining a lower and thus more stable actual clock frequency of 100 MHz to 400 MHz.
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