Number of memory modules

Ein Speichermodul oder Speicherriegel ist eine kleine Leiterplatte, auf der mehrere Speicherbausteine (Dynamisches RAM in Form von integrierten Schaltkreisen) aufgelötet sind. Speichermodule bilden oder erweitern den Arbeitsspeicher elektronischer Geräte wie Computer oder Drucker und werden dort in speziell dafür vorgesehene Steckplätze gesteckt.

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Memory type

DDR-SDRAM ("Double Data Rate Synchronous Dynamic Random Access Memory") is a type of random access memory (RAM) currently available in three categories. DDR-SDRAM with 184 contacts, DDR2-SDRAM with 240 contacts and DDR3-SDRAM also with 240 contacts. They are mainly used for memory modules of the DIMM or SO-DIMM standard as main memory in PCs and laptops.

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Memory chip

Random-access memory is a form of computer data storage. A random-access device allows stored data to be accessed directly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations. Therefore the time to access a given data location varies significantly depending on its physical location.

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Memory form factor

A DIMM or dual in-line memory module, comprises a series of dynamic random access memory integrated circuits. These modules are mounted on a printed circuit board and designed for use in personal computers, workstations and servers. DIMMs began to replace SIMMs (single in-line memory modules) as the predominant type of memory module as Intel P5-based Pentium processors began to gain market share.

The main difference between SIMMs and DIMMs is that DIMMs have separate electrical contacts on each side of the module, while the contacts on SIMMs on both sides are redundant. Another difference is that standard SIMMs have a 32-bit data path, while standard DIMMs have a 64-bit data path.

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RAM buffer

In addition to bandwidth and capacity variants, modules can
1. Optionally implement ECC, which is an extra data byte lane used for correcting minor errors and detecting major errors for better reliability. Modules with ECC are identified by an additional ECC in their designation.
2. Be "registered", which improves signal integrity (and hence potentially clock speed and physical slot capacity) by electrically buffering the signals at a cost of an extra clock of increased latency. Those modules are identified by an additional R in their designation, whereas non-registered (a.k.a. "unbuffered") RAM may be identified by an additional U in the designation.
3. Be Fully buffered modules, which are designated by F or FB and do not have the same notch position as other classes. Fully buffered modules cannot be used with motherboards that are made for registered modules, and the different notch position physically prevents their insertion.

CAS latency

CAS latency is the delay time which elapses between the moment a memory controller tells the memory module to access a particular column in a selected row, and the moment the data from the given array location is available on the module's output pins.

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tRCD

Der Parameter tRCD (RAS-to-CAS delay, row-to-column delay) beschreibt bei einem DRAM die Zeit, die nach der Aktivierung einer Wortleitung (activate) verstrichen sein muss, bevor ein Lesekommando (read) gesendet werden darf.

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tRAS

Der Parameter tRAS (RAS pulse width, Active Command Period, Bank Active Time) beschreibt die Zeit, die nach der Aktivierung einer Zeile (bzw. einer Zeile in einer Bank) verstrichen sein muss, bevor ein Kommando zum Deaktivieren der Zeile (Precharge, Schließen der Bank) gesendet werden darf.

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tRP

Der Parameter „tRP“ („Row Precharge Time“) beschreibt die Zeit, die nach einem Precharge-Kommando mindestens verstrichen sein muss, bevor ein erneutes Kommando zur Aktivierung einer Zeile in der gleichen Bank gesendet werden darf.

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XMP

Extreme Memory Profiles (XMP) sind von Intel eingeführte Zertifizierungen für DDR3-Speichermodule aus dem PC-Bereich.

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Voltage

The voltage between two points is a short name for the electrical force that would drive an electric current between those points. Specifically, voltage is equal to energy per unit charge. In the case of static electric fields, the voltage between two points is equal to the electrical potential difference between those points. In the more general case with electric and magnetic fields that vary with time, the terms are no longer synonymous.

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