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Table of contents
Bit - The smallest unit of binary data, assumes the value of either 1 or 0.
DDR3 - Third generation DDR memory leaps greatly forward in terms of data transfer rate and power management. DDR3 provides even higher bandwidth than DDR2 memory due to the 8-bit prefetch buffer (4-bit prefetch of DDR2, and 2-bit of DDR). The advanced fabrication technology allows lower operating currents and voltages (1.5V, compared to 1.8V in DDR2) and thus enhances thermal performance.
DIMM - Dual In-Line Memory Module: Circuit board where RAM memory chips are mounted. A DIMM is capable of transferring 64 bits of data in a cycle.
Latency/ Timing – Latency is the time delay between a request to access memory and the actual output of the data, measured in clock cycles. There are several different types of latencies used to measure memory performance. These latency figures are often called memory timing. The most important memory latency is CAS Latency.
PCB - Printed Circuit Board: A fiberglass board with electrical traces to place and connect chips and other electronic components.
RAM - Random Access Memory: Used by a computer system as main memory to temporarily store data. Most contemporary RAM is volatile memory, i.e. the information will be lost when power is disrupted or shut off.
RAS - Row Address Strobe: A signal that indicates to DRAM a particular address as a row address, see CAS for more details.
RDRAM - Rambus Dynamic Random Access Memory: This is a type of synchronous DRAM, created by the Rambus Corporation. RDRAM features an architecture designed to achieve high bandwidth. It is used in the Sony PlayStation 2, early Pentium 4 desktop systems and other places. The XDR DRAM, RDRAM's successor, is used in IBM's Cell processor and the Sony PlayStation 3.
Registered/Unbuffered Memory - Almost all system memory in PCs today is unbuffered memory. With increasing system memory, stability and performance deterioration is inevitable since the memory controller has to address each memory chip on all modules directly. To solve this problem, higher density systems use registered memory instead, which contains registers as buffers to temporarily hold data for one clock cycle before it is transferred. This increases the reliability of high-speed data access to high density memory but sacrifices some performance. Registered memory modules are typically used only in servers and other mission-critical systems where it is extremely important that data is properly handled.
SDRAM - SDRAM has a synchronous interface. It waits for a clock pulse before transferring data and is therefore synchronous with the computer system bus and processor. This greatly improves performance over asynchronous DRAM. SDRAM is not as popular as it once was and may be used during upgrades. SDRAM modules usually come in the form of 168-pin DIMMs.
SO-DIMM - Small Outline Dual Inline Memory Module: A memory form factor that is significantly smaller than DIMM. It is often used in notebook computers and some other small form factor systems.
SPD - Serial Presence Detect: JEDEC standards require certain parameters to be stored in the EEPROM (electrically erasable programmable read-only memory) located on a memory module. This combination of parameters is called SPD information. Memory timing, manufacturer, speed, serial number and other useful information are contained in SPD information, and can be accessed via BIOS (basic input/output system).
SRAM - Static Random Access Memory: Unlike DRAM, there are only several transistors used in the memory cells of SRAM, with no capacitors involved. Thus SRAM do not require refreshing. This results in much higher performance, but SRAM is much more expensive than DRAM, and therefore is not utilized in the capacities that DRAM is. SRAM is used primarily for cache applications (e.g. CPU L1 Cache).