Memory physical types

RAM vs SAM (random addresses vs serial addresses(tape) )

DRAM vs SRAM
*Dynamic(keep refreshed the voltage, up to 1000times/sec)
*Static (need not refreshed, so faster but more expensive)

Note : memory chips containing transistors (each transistor has capacitor for storing electric as represent of bit 1), the transistor function as switch, 0 or 1. Transistor has Base, C and Emitter. These 3 legs make a transistors as electronic switch.

DRAM vs SDRAM
* Synchronous : faster and more expensive (it has feature pipelines, where it can do next task without wait the prev one). The sync is about time clock, so it has cycle to do actions.

== Pipelining means that the chip can accept a new instruction before it has finished processing the previous one. In a pipelined write, the write command can be immediately followed by another instruction without waiting for the data to be written to the memory array. In a pipelined read, the requested data appears after a fixed number of clock pulses after the read instruction, cycles during which additional instructions can be sent. (This delay is called the latency and is an important parameter to consider when purchasing SDRAM for a computer.) ====

Complete on : http://en.wikipedia.org/wiki/Synchronous_dynamic_random_access_memory


DIMM vs SIMM
* dual inline memory module



DDR (dual data rate)vs SDR (single)
*


DDR2 ( is then DDR1)
DDR3 (is faster in transfer than DDR2)



x4 vs x8 (by 4 vs by 8)