Page 196 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

Memory ICs 177

Whatever flavor of DRAM you are (that is, the pads on opposite sides
using, a single device can on of the board are “tied together”).
contain a limited amount of By comparison, in the case of a
so a number of DRAMS are gath- dual in-line memory module (DIMM),
ered together onto a small circuit the pads on opposite sides of the
board called a memory module. board are electrically isolated from
Each memory module has a line each other and form two separate
of gold-plated pads on both sides contacts.
of one edge of the board. These Last but not least, we have the
pads plug into a corresponding RIMM, which really doesn‘t stand
connector on the main computer for anything per se, but which is
board. the trademarked name for a
A single in-line Rambus memory module (RIMMs
(SIMM) has the same electrical are similar in concept to DIMMs,
signal on corresponding pads but have a different pin count and
the front and back of the board configuration).

thin insulating layer. A memory cell is created by the intersection of two wires
(say a “row” line and a “column” line) with an MJT sandwiched between them.
MRAMs have the potential to combine the high speed of SRAM, the storage
capacity of DRAM, and the non-volatility of FLASH, while consuming very
little power. It’s taken close to 30 years, but MRAMs test chips are predicted to
become available around 2003, with volume production in 2004.

nvRAMs
Finally, a class of devices known as nonuohtile RAMS (~vRAMs)~’ may be
used in cases where high speed is required and cost is not an overriding issue.
These devices are generally formed from an SRAM die mounted in a package
with a very small battery, or as a mixture of SRAM and E2PROM cells fabri-
cated on the same die.

21 In conversation, nvRAM is pronounced as “n-v-RAM.” That is, spelling out the “n” and the
“v” and following them with “RAM to rhyme with “ham.”