Computer Memory

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  • Topic: Computer memory, Flash memory, Non-volatile memory
  • Pages : 7 (2207 words )
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  • Published : July 31, 2011
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Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, unlike non-volatile memory which does not require a maintained power supply. It has been less popularly known as term Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Since real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory. The main memory (the "RAM") in personal computers is Dynamic RAM (DRAM), as is the "RAM" of home game consoles (PlayStation, Xbox 360 and Wii), laptop, notebook and workstation computers. Here are the types of volatile memory:

The advantage of DRAM is its structural simplicity: only one transistor and a capacitor are required per bit, compared to six transistors in SRAM. This allows DRAM to reach very high density. Unlike flash memory, it is volatile memory (cf. non-volatile memory), since it loses its data when power is removed. The transistors and capacitors used are extremely small—millions can fit on a single memory chip.

Double data rate synchronous dynamic random access memory (DDR SDRAM) is a class of memory integrated circuits used in computers. Compared to single data rate (SDR) SDRAM, the DDR SDRAM interface makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals. Implementations often have to use schemes such as phase-locked loops and self-calibration to reach the required timing accuracy.The interface uses double pumping (transferring data on both the rising and falling edges of the clock signal) to lower the clock frequency. One advantage of keeping the clock frequency down is that it reduces the signal integrity requirements on the circuit board connecting the memory to the controller. The name "double data rate" refers to the fact that a DDR SDRAM with a certain clock frequency achieves nearly twice the bandwidth of a single data rate (SDR) SDRAM running at the same clock frequency, due to this double pumping

Static random access memory (SRAM) is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM (DRAM), it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit. SRAM exhibits data remanence, but is still volatile in the conventional sense that data is eventually lost when the memory is not powered. Each bit in an SRAM is stored on four transistors that form two cross-coupled inverters. This storage cell has two stable states which are used to denote 0 and 1. Two additional access transistors serve to control the access to a storage cell during read and write operations. A typical SRAM uses six MOSFETs to store each memory bit. In addition to such 6T SRAM, other kinds of SRAM chips use 8T, 10T, or more transistors per bit.

Upcoming Volatile Memory:

T-RAM, short for "Thyristor RAM" or "thyristor random-access memory", is a new type of DRAM computer memory invented and developed by T-RAM Semiconductor, which departs from the usual designs of memory cells, combining the strengths of the DRAM and SRAM: high speed and high volume. This technology, which exploits the electrical property known as negative differential resistance and is called Thin-Capacitively-Coupled-Thyristor, is used to create memory cells capable of very high packing densities. Due to this, this memory is highly scalable, and already has a storage density that is several times higher than found in conventional six-transistor SRAM memory. It is expected that the next generation of T-RAM memory will have the same density as DRAM. It is assumed that this type of memory will be used in the next-generation processors by AMD,...
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