Updated: 2021-11-19

S = static, D = dynamic

how to store data transistors capacitors
periodically refresh not needed needed
speed faster slower
cost expensive cheaper
power consumption lower higher
usage microprocessor caches main memory
capcity lower (in MBs) higher (in GBs)
placement processors motherboard


  • DRAM needs periodically refreshed since capacitors leak power, and it is sensitive to electrical noise. SRAM: No charge leakage since it changes direction of current through switches instead of leaking power through the capacitor.


Synchronous Dynamic Random Access Memory (SDRAM) is a type of DRAM that synchronizes with the CPU’s clock cycles, so the memory controller knows exactly when requested data will be ready to access. This cuts access time and improves memory performance.

DDR – The latest generation of SDRAM is Double Data Rate (DDR). DDR increases speed, reduces power consumption, introduces refresh mechanisms, and adds security functions such as CRC.