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dram:see English units of measurementEnglish units of measurement,
principal system of weights and measures used in a few nations, the only major industrial one being the United States. It actually consists of two related systems—the U.S.
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(drachm; Russian drakhma, from Greek drachme).
(1) A unit in the now outmoded system of apothecaries’ weights. An apothecaries’ dram was one-eighth of an ounce and contained three scruples; the Russian apothecaries’ dram was the equivalent of 3.732 g. In the English system of measurement an apothecaries’ dram equaled 3.888 g.
(2) A fluidram, a measure of displacement used in the USA, equal to 3.6966 milliliters.
(3) In the avoirdupois system, a measure of weight equaling one-sixteenth of an ounce, 1.772 g.
dynamic RAMThe most common type of computer memory and generally available today in the form of synchronous dynamic RAM chips (see SDRAM). Most all volatile memory is dynamic RAM because it uses only one transistor and one storage capacitor for each bit. It is denser and much less costly than "static RAM," its faster counterpart.
Dynamic RAM Is a Total Loser
Unlike non-volatile firmware chips (flash, ROM, EEPROM, etc.), which hold their contents when the power is turned off, both dynamic RAM (DRAM) and static RAM (SRAM) require constant power.
The capacitors in a dynamic RAM chip are electrical storage tanks that do a poor job of holding a charge. They constantly leak, and the memory chip would lose its content were it not for the refresh circuitry that continuously re-energizes the capacitors approximately 15 times per second.
In 1968, dynamic RAM was patented by IBM, and the first commercial chips came from Intel and Mostek in the early 1970s with a capacity of 1,000 bits. See static RAM and memory types.
|A Dynamic RAM Cell|
|DRAM cells are very simple. The combination of voltage on the row and column lines charges a capacitor. The only problem is that the capacitors keep losing their charges, and the bits must be read and re-written to the same state several times each second.|