Hardware Reference
In-Depth Information
port DDR3. In 2009, with full support from both Intel and AMD, DDR3 finally began to
achieve price parity with DDR2, causing DDR3 to begin to eclipse DDR2 in sales.
DDR3 modules use advanced signaling techniques, including self-driver calibration and
datasynchronization,alongwithanoptionalonboardthermalsensor.DDR3memoryruns
on only 1.5V, which is nearly 20% less than the 1.8V that DDR2 memory uses. The lower
voltagecombinedwithhigherefficiencyreducesoverallpowerconsumptionbyupto30%
compared to DDR2.
The 240-pin DDR3 modules are similar in pin count, size, and shape to the DDR2 mod-
ules; however, the DDR3 modules are incompatible with the DDR2 circuits and are de-
signed with different keying to make them physically noninterchangeable.
DDR3 modules are available in speeds of 800MHz (effective) and higher. Just as with
DDR and DDR2, the true clock speed is half the effective rate, which is technically ex-
pressed in million transfers per second (MTps).
Table 6.9
shows the JEDEC-approved
DDR3 module types and bandwidth specifications.
Table 6.9 JEDEC Standard DDR3 Module (240-Pin DIMM) Speeds and Transfer Rates
ThefastestofficialJEDEC-approvedstandardisDDR3-2133,whichiscomposedofchips
that run at an effective speed of 2,133MHz (really megatransfers per second), resulting in
modules designated PC3-17000 and having a bandwidth of 17,066MBps. However, just
as with DDR and DDR2, many manufacturers produce nonstandard modules designed
for overclocked systems. These are sold as modules with unofficial designations, clock
speeds, and performance figures that exceed the standard ratings.
Table6.10
showsthepopularunofficialDDR3speedratingsI'veseenonthemarket.Note
that because the speeds of these modules don't conform to the standard default mother-
