Three years ago, there wasn't much to say about sytem RAM. Almost all PCs came with fast page mode (FPM) DRAM, which ran at speeds between 100ns and 80ns. However, escalating CPU and motherboard bus speeds outstripped the ability of FPM DRAM to deliver data in a timely manner. Nowadays there are a lot of different memory designs.
Due to cost considerations, all but the very high-end (and very expensive) computers have utilized DRAM for main memory. Originally, these were asynchronous, single-bank designs because the processors were relatively slow. Most recently, synchronous interfaces have been produced with many advanced features. Though these high-performance DRAMs have been available for only a few years, it is apparent that they will soon be replaced by at least one of the protocol-based designs, such as SyncLink or the DRDRAM design from Rambus, Inc. and Intel.