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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.
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