Dynamic random access memory (DRAM) is a type of memory that is typically used for data or program code that a computer processor needs to function. DRAM is a common type of random access memory used in personal computers (PCs), workstations and servers.
SDR SDRAM (Single Data Rate synchronous DRAM) This type of SDRAM is slower than the DDR variants, because only one word of data is transmitted per clock cycle (single data rate). But this type is also faster than its predecessors EDO-RAM and FPM-RAM which took typically 2 or 3 clocks to transfer one word of data.
SRAM (static RAM) is random access memory that retains data bits in its memory as long as power is being supplied. Unlike dynamic RAM (DRAM), which stores bits in cells consisting of a capacitor and a transistor, SRAM does not have to be periodically refreshed.
Synchronous dynamic random access memory (SDRAM) is dynamic random access memory (DRAM) with an interface synchronous with the system bus carrying data between the CPU and the memory controller hub. SDRAM has a rapidly responding synchronous interface, which is in sync with the system bus. SDRAM waits for the clock signal before it responds to control inputs.