Specifications

Computer Architecture and Maintenance (G-Scheme-2014)
DDR2 SDRAM
DDR2 SDRAM is very similar to
DDR SDRAM, but doubles the
minimum read or write unit again,
to 4 consecutive words. The bus
protocol was also simplified to
allow higher performance
operation. (In particular, the "burst
terminate" command is deleted.)
This allows the bus rate of the
SDRAM to be doubled without
increasing the clock rate of internal
RAM operations; instead, internal
operations are performed in units 4
times as wide as SDRAM. Also, an
extra bank address pin (BA2) was
added to allow 8 banks on large
RAM chips.
Typical DDR2 SDRAM clock rates are 200, 266, 333 or 400 MHz (periods of 5, 3.75, 3
and 2.5 ns), generally described as DDR2-400, DDR2-533, DDR2-667 and DDR2-800
(periods of 2.5, 1.875, 1.5 and 1.25 ns). Corresponding 240-pin DIMMS are known as
PC2-3200 through PC2-6400. DDR2 SDRAM is now available at a clock rate of 533 MHz
generally described as DDR2-1066 and the corresponding DIMMs are known as PC2-
8500 (also named PC2-8600 depending on the manufacturer).
Note that because internal operations are at 1/2 the clock rate, DDR2-400 memory
(internal clock rate 100 MHz) has somewhat higher latency than DDR-400 (internal
clock rate 200 MHz).
Features of DDR-2
i. It is 240 pin module
ii. Speed – 400Mhz , 533Mhz,667Mhz and above
iii. High Bandwidth
iv. Synchronous Architecture
v. Operating at 1.8V
vi. Prefetch 4bit at a time
Prepared By – Prof. Manoj.kavedia (9860174297 – 9324258878 ) (www.kavediasir.yolasite.com)
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