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5.4. OTHER MEMORY TECHNOLOGIES YOU MAY HAVE HEARD ABOUT
ENHANCED SDRAM (ESDRAM)In order to increase the speed and efficiency of standard memory modules, some manufacturers have incorporated a small amount of SRAM directly into the chip, effectively creating an on-chip cache. ESDRAM is essentially SDRAM, plus a small amount of SRAM cache, which allows for burst operations of up to 200MHz. Just as with external cache memory, the goal of cache DRAM is to hold the most frequently used data in the SRAM cache to minimize accesses to the slower DRAM. One advantage of on-chip SRAM is that it enables a wider bus between the SRAM and DRAM, effectively increasing the bandwidth and speed of the DRAM.
FAST CYCLE RAM (FCRAM)FCRAM, co-developed by Toshiba and Fujitsu, is intended for specialty applications such as high-end servers, printers, and telecommunications switching systems. It includes memory array segmentation and internal pipelining that speed random access and reduce power consumption.
SYNCLINK DRAM (SLDRAM)Though considered obsolete today, SLDRAM was developed by a consortium of DRAM manufacturers as an alternative to Rambus technology in the late 1990s.
VIRTUAL CHANNEL MEMORY (VCM)Developed by NEC, VCM allows different "blocks" of memory to interface inde-pendently with the memory controller, each with its own buffer. This way, different system tasks can be assigned their own "virtual channels," and information related to one function does not share buffer space with other tasks occurring at the same time, making operations more efficient.