DDRAM: – Short for Double Data Rate-Synchronous DRAM, a type of SDRAM that supports data transfers on both edges of each clock cycle (the rising and falling edges), effectively doubling the memory chip’s data throughput. DDR-SDRAM also consumes less power, which makes it well suited to notebook computers. DDR-SDRAM is also called SDRAM II And DDRAM.
FPMDRAM: – (Fast Page Mode Dynamic Random Access Memory) This type of memory is slightly faster than DRAM. It allows for a burst cycle, which increases the speed of subsequent accesses to the memory after the initial read. EDO DRAM is generally replacing FPM DRAM. Prior to newer forms of dynamic random access memory (DRAM), FPM DRAM (Fast Page Mode DRAM) was the most common kind of DRAM in personal computers. Page mode DRAM essentially accesses a row of RAM without having to continually re-specify the row. A row access strobe (RAS) signal is kept active while the column access strobe (CAS) signal changes to read a sequence of contiguous memory cells. This reduces access time and lowers power requirements. Clock timings for FPM DRAM are typically 6-3-3-3 (meaning 3 clock cycles for access setup, and 3 clock cycles for the first and each of three successive accesses based on the initial setup).