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Dynamic random-access memory facts for kids

Kids Encyclopedia Facts

Dynamic random access memory is the most commonly used form of RAM.

DRAM is called dynamic (or active), because it must be refreshed all the time or it will lose the data which it is supposed to be storing. Because it loses data when power is removed, DRAM is called volatile. This word comes from the Latin adjective volātilis, which means "flying, fleeting, transitory".

Refreshing DRAM means reading the data from the DRAM and directly writing them back to the DRAM. DRAM is made up of millions of very small capacitors. Each of these capacitors has a transistor to let energy in and out. The capacitor slowly loses energy, and if the DRAM is not refreshed, in the end one or more of the capacitors will let so much energy out, that for example a 1 will become a 0, so data will be lost or corrupted. Almost all computers refresh their DRAM many times per second.

Comparison DRAM and SRAM

DRAM is often compared to SRAM (Static RAM). SRAM is able to store data as long as power/energy is used. There is no need to refresh it. SRAM can also be faster than DRAM. But SRAM is much more expensive than DRAM. Also, SRAM uses more electric power and heats up much faster than DRAM. DRAM and SRAM lose the data when the power to them is turned off, unlike non-volatile random-access memory.

Images for kids

  • MT4C1024-HD

    A die photograph of the Micron Technology MT4C1024 DRAM integrated circuit (1994). It has a capacity of 1 megabit equivalent of 2^{20}bits or 128 kB.

  • NeXTcube motherboard

    Motherboard of the NeXTcube computer, 1990, with 64 MiB main memory DRAM (top left) and 256 KiB of VRAM (lower edge, right of middle).

  • Square array of mosfet cells read

    The principles of operation for reading a simple 4 \times4 DRAM array

  • DRAM cell field (details)

    Basic structure of a DRAM cell array

  • Square array of mosfet cells write

    Writing to a DRAM cell

  • DRAM self-aligned storage node locations

    Self-aligned storage node locations simplify the fabrication process in modern DRAM.

  • Pair32mbEDO-DRAMdimms

    A pair of 32 MB EDO DRAM modules

  • SAMSUNG@DDR-SDRAM@64MBit@K4D62323HA-QC60 Stack-DSC03539-DSC03556 - ZS-DMap

    The die of a Samsung DDR-SDRAM 64MBit package

  • Sapphire Ultimate HD 4670 512MB - Qimonda HYB18H512321BF-10-93577

    A 512 MBit Qimonda GDDR3 SDRAM package

  • SAMSUNG@QDDR3-SDRAM@256MBit@K5J55323QF-GC16 Stack-DSC01340-DSC01367 - ZS-retouched

    Inside a Samsung GDDR3 256 MBit package

  • Olivetti JP90 - Toshiba TC518129CFWL-80 on controller-8514

    1 Mbit high speed CMOS pseudo static RAM, made by Toshiba

See also

Kids robot.svg In Spanish: DRAM para niños

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