5.1 DYNAMIC RAMS (DRAMS)
Dynamic random access memory (DRAM) is memory that uses charge storage on a capacitor as an equivalent to binary data. The data can be accessed at any memory cell randomly rather than having to proceed sequentially from a starting cell. DRAM needs to have its storage cells refreshed (given a new electronic charge periodically) (Sharma, 1997). Compared with SRAM, DRAM has smaller structures and lower prices, but is slower. To compensate for the slower spend, synchronous dynamic random access memory (SDRAM) and double data rate (DDR) access types were introduced.
DRAMs are used as the main memory in most memory systems and have the highest volume production, covering about 16.2 percent of the total semiconductor market in 2006 (McClean et al., 2007). DRAM represents the least expensive form of random access semiconductor memory. DRAM belongs to the volatile memory family because data is lost when power is removed.
5.1.1 Types of DRAMs
There are two categories of DRAM: asynchronous DRAM and synchronous DRAM, also referred to as SDRAM. Each category can again be further divided into a JEDEC standard conform memory and manufacturer-specific memory.
The main types of JEDEC standard conform asynchronous DRAM include fast page mode (FPM), extended data out (EDO), and burst mode (BM). The market share of FPM and EDO is no longer noteworthy, with only a few manufacturers still offering these in 2010 (Memphis, 2010a). BM never had a major market share. Manufacturer-specific ...