In many computer systems, memory is the bottleneck — speeding the memory system
improves overall performance. As a result, engineers have concentrated on
memory technologies with lower cycle times. One approach uses a technique that runs
the memory system at a multiple of the normal clock rate (e.g., double). Because the
clock runs faster, the memory can deliver data faster. Therefore, the technologies are
known as fast data rate memories, typically double data rate or quadruple data rate.