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RAM types

The traditional RAM type is DRAM (dynamie RAM). The other type is SRAM (static RAM). SRAM continues to remember its content, while DRAM must be refreshed every few milli seconds. DRAM consists of micro capacitors, while SRAM consists of off/on switches. Therefore, SRAM can respond much faster than DRAM. SRAM can be madę with a rise time as short as 4 ns. It is used in different versions in L2 cache RAM (for ex ample/we linę BURST Cache SRAM).

DRAM is by far the cheapestto build. Newer and faster DRAM types are developed continuously. Currently, there are at leastfour types:

■    FPM (Fast Page Modę)

Clock speed	Time per clock tick
20 MHz	50 ns
25 MHz 1 ‘	40 JTS_|
33 MHz	30 ns
50 MHz 1	20 ns |
66 MHz	15 ns |
100 MHz	10 ns
133 MHz	6 ns

■    ECC (Error Correctmg Codę)

• EDO (Extended Data Output)

■    SDRAM (Synchronous Dynamie RAM)