DDR-3
DDR-3, the third-generation of DDR SDRAM technology, will make further improvements in bandwidth
and power consumption. Manufacturers of DDR-3 will initially use 90 nm fabrication technology and
move toward 70 nm as production volumes increase. DDR-3 will operate at clock rates from 400
MHz to 800 MHz with theoretical peak bandwidths ranging from 6.40 GB/s to 12.8 GB/s. DDR-3 is
expected to reduce power consumption by up to 30% compared to a DDR-2 DIMM operating at the
same speed. DDR-3 DIMMs are expected to use the same 240-pin connector as DDR2 DIMMs, but the
key notch will be in a different position.
To increase performance and reduce power consumption of DDR-3, designers made several key
enhancements, including:
• An 8-bit prefetch buffer, compared to the 4-bit buffer for DDR-2, storing more data before it is
needed.
• Fly-by topology (for the commands, addresses, control signals, and clocks) improves signal integrity
by reducing the number of stubs and their length. This feature requires the controller to support
"write leveling" on DDR-3 DIMMs.
• 1.5-V signaling (compared to 1.8 V for DDR-2) for lower power consumption
• A thermal sensor integrated on the DIMM module signals the chipset to throttle memory traffic to the
DIMM if its temperature exceeds a programmable critical trip point.
Module naming convention and peak bandwidth
Table 1 summarizes the various types of DDR-1, DDR-2, and DDR-3 SDRAM and their associated
naming conventions. Originally, the module naming convention for DDR-SDRAM was based on the
effective clock rate of the data transfer: PC200 for DDR SDRAM that operates at 100 MHz; PC266
for 133 MHz; and so forth. But after confusion arose over the Rambus naming convention, the
industry based the DDR-SDRAM naming convention on the actual peak data transfer rate in MB/s. For
example, PC266 is equivalent to PC2100 (64 bit * 2 * 133 MHz = 2.1 GB/s or 2100 MB/s).
Table 1. Summary of DDR SDRAM technologies
Type
Component
naming
convention
DDR-1
DDR200
DDR266
DDR333
DDR400
DDR-2
DDR2-400
DDR2-533
DDR2-667
DDR2-800
DDR-3
DDR3-800
DDR3-1066
DDR3-1333
DDR3-1600
Module naming
Bus speed
convention
PC1600
100 MHz
PC2100
133 MHz
PC2700
166 MHz
PC3200
200 MHz
PC2-3200R
200 MHz
PC2-4300
266 MHz
PC2-5300
333 MHz
PC2-6400
400 MHz
PC3-6400
400 MHz
PC3-8500
533 MHz
PC3-10600
667 MHz
PC3-12800
800 MHz
Peak bandwidth
1.6 GB/s
2.1 GB/s
2.7 GB/s
3.2 GB/s
3.2 GB/s
4.3 GB/s
5.3 GB/s
6.4 GB/s
6.4 GB/s
8.5 GB/s
10.6 GB/s
12.8 GB/s
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