SDR memory (front only shown) has 168 pins and two notches.

SDR SDRAM is Single Data Rate synchronous dynamic random access memory, a type of computer memory. The term is used to contrast with Double Data Rate SDRAM, or DDR SDRAM, but since single data rate SDRAM was the only sort available when SDRAM was introduced, is simply called "SDRAM", rather than "SDR SDRAM". Image File history File links Download high resolution version (1746x486, 149 KB) Summary This image is simply to illustrate the physical characteristics of SDR SDRAM (e. ... Image File history File links Download high resolution version (1746x486, 149 KB) Summary This image is simply to illustrate the physical characteristics of SDR SDRAM (e. ... Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor. ... The terms storage (U.K.) or memory (U.S.) refer to the parts of a digital computer that retain physical state (data) for some interval of time, possibly even after electrical power to the computer is turned off. ... DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. ...

While other forms of DRAM have an asynchronous interface, meaning that it reacts immediately to changes in its control inputs, SDRAM has a synchronous interface, meaning that it waits for a clock pulse before responding to its control inputs- it synchonizes with the computer's system bus, and thus with the processor. The clock is used to drive an internal finite state machine that can pipeline incoming commands. This allows the chip to have a more complex pattern of operation than plain DRAM. Dram can mean several things: for the imperial unit of volume see dram (volume) for the imperial unit of weight or mass see avoirdupois and apothecaries system of mass for the Armenian monetary unit see dram (currency) DRAM is a type of RAM and unlike dram is spelled in all... In synchronous digital electronics, such as most computers, a clock signal is a signal used to coordinate the actions of two or more circuits. ... Fig. ...

Pipelining means that the chip can accept a new command before it has finished processing the previous one. In a pipelined write, the write command can be immediately followed by another command without waiting for the data to be written to the memory array. In a pipelined read, the requested data appears a fixed number of clock pulses after the read command. It is not necessary to wait for the data to appear before sending the next command. This delay is called the latency, and is an important parameter to be considered when purchasing SDRAM for your computer. RAM Latency is the amount of wait time that a computer experiences when trying to access data in its RAM. RAM latency is measured in front side bus clock cycles. ...

SDRAM for PCs is rated for its potential maximum clock rate. Speeds included PC66, PC100, and PC133, representing 66, 100 and 133 megahertz. There were additional unofficial speeds for enthusiast SDRAM parts, such as PC150, for 150 MHz. SDRAM comes in 168-pin DIMMs for desktops, or 144-pin SODIMMs mainly used in laptops, while DDR SDRAM comes in 184-pin DIMMs, and DDR2 uses a 240-pin configuration. MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... Two types of DIMMs: a 168-pin SDRAM module (top) and a 184-pin DDR SDRAM module (bottom). ... A type of computer memory integrated circuit, a SO-DIMM (from Small Outline DIMM) is a smaller alternative to a DIMM. As a result of being roughly half the size of regular DIMMs, SO-DIMMs are often utilised in laptop computers. ...

SDRAM was introduced in 1997, and by 2000 had replaced all other types of DRAM in modern computers, because of its greater speed, and much lower latency.

SDRAM is also available in registered memory varieties, for systems that need greater scalability. Registered (sometimes called buffered) memory modules have additional components between the SDRAM modules and the systems memory controller. ...

Currently, 168-pin SDRAM type is not used in new PC systems, and PCs come with DDR or DDR2 SDRAM, with DDR2 quickly phasing out DDR.

See also

• Random access memory (RAM)
• Static RAM (SRAM)
• Non-Volatile RAM (NVRAM)
• Dynamic RAM (DRAM)
  • Fast Page Mode DRAM
  • EDO RAM or Extended Data Out DRAM
  • XDR DRAM
  • SDRAM or Synchronous DRAM
    • DDR SDRAM or Double Data Rate Synchronous DRAM; now being replaced by DDR2
    • RDRAM or Rambus DRAM

To meet Wikipedias quality standards, this article or section may require cleanup. ... A six-transistor CMOS SRAM cell. ... Non-Volatile Random Access Memory (NVRAM) is a computer memory chip which will not lose its information when the power is lost. ... Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor. ... DRAM is a type of random access memory that stores each bit of data in a separate capacitor. ... DRAM is a type of random access memory that stores each bit of data in a separate capacitor. ... XDR DRAM is a high performance RAM Interface like SDR-SDRAM and DDR-SDRAM. The XDR solution was engineered to be effective in small high-bandwidth consumer systems, high-performance main memory applications, and flagship GPUs. ... DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Rambus Incorporated NASDAQ: RMBS (founded 1990) is a provider of high-speed interface technology, most notably their Rambus Direct RAM memory technology, which was intended to replace SDRAM and challenge DDR RAM as the standard memory used in computers. ...

External links

• How RAM works
• What is RAM