''Memory latency'' is the time (the
latency) between initiating a request for a
byte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...
or word in memory until it is retrieved by a
processor
Processor may refer to:
Computing Hardware
* Processor (computing)
**Central processing unit (CPU), the hardware within a computer that executes a program
*** Microprocessor, a central processing unit contained on a single integrated circuit (I ...
. If the data are not in the
processor's cache, it takes longer to obtain them, as the processor will have to communicate with the external
memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remember ...
cells. Latency is therefore a fundamental measure of the speed of memory: the less the latency, the faster the reading operation.
Latency should not be confused with
memory bandwidth, which measures the
throughput
Network throughput (or just throughput, when in context) refers to the rate of message delivery over a communication channel, such as Ethernet or packet radio, in a communication network. The data that these messages contain may be delivered ove ...
of memory. Latency can be expressed in clock cycles or in time measured in nanoseconds. Over time, memory latencies expressed in clock cycles have been fairly stable, but they have improved in time.
[Crucial Technology, "Speed ''vs.'' Latency: Why CAS latency isn't an accurate measure of memory performance]
/ref>
See also
* Burst mode (computing)
* CAS latency
* Multi-channel memory architecture
* Interleaved memory
In computing, interleaved memory is a design which compensates for the relatively slow speed of dynamic random-access memory (DRAM) or core memory, by spreading memory addresses evenly across memory banks. That way, contiguous memory reads and w ...
* SDRAM burst ordering
* SDRAM latency
References
External links
Overview of the different kinds of Memory Latency
Article and Analogy of the Effects of Memory Latency
Computer memory
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