DRAM is one option of semiconductor memory that a system designer can use when building a computer. Alternative memory choices include static RAM (SRAM), electrically erasable programmable read-only memory (EEPROM), NOR flash and NAND flash. Many systems use more than one type of memory.
The main advantages of DRAM are its simple design, speed and low cost in comparison to alternative types of memory. The main disadvantages of DRAM are volatility and high power consumption relative to other options.
There are many types or interfaces for communicating with DRAM. They include fast page mode DRAM (FPM DRAM), extended data out DRAM (EDO RAM) and synchronous DRAM (SDRAM). SDRAM is a generic name for types of DRAM synchronized with the clock speed of the microprocessor. They include single data rate (SDR) SDRAM, double data rate (DDR) SDRAM, DDR2 SDRAM, DDR3 SDRAM and DDR4 SDRAM.
DRAM vs. SRAM
DRAM is a successor to SRAM. Memory designers reduced the number of elements per bit and eliminated differential bit lines to save chip area to create DRAM. As a result, DRAM is less expensive to produce than SRAM.
But SRAM retains some advantages over DRAM. SRAM does not need to be refreshed because it operates on the principle of switching the current flow in one of two directions rather than holding a charge in place within a storage cell. SRAM is generally used for cache memory, which can be accessed more quickly than DRAM.
SRAM is capable of byte-level reads and writes, and is faster at reads and writes than DRAM. DRAM writes data at the byte-level and reads at the multiple-byte page level.
Power differences vary based on whether the system is in active or sleep mode. DRAM requires less power than SRAM in an active state, but SRAM consumes considerably less power than DRAM does while in sleep mode.