Ddr3 memory types

Written by g.d. palmer
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Ddr3 memory types
DDR3 memory has a different pattern of notches than other, older memory chips. (Ryan McVay/Photodisc/Getty Images)

Double Data Rate 3 memory, also called DDR3, is a type of SDRAM that offers larger rates of data transfer than earlier memory types. This memory is incompatible with earlier types of RAM and uses a differently-shaped slot on the motherboard. DDR3 memory also offers reduced power consumption over earlier memory specifications.

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DDR3-800 memory is the slowest type of DDR3 RAM. It has a 100 megahertz memory clock and a 10 nanosecond cycle time, with a 400MHz I/O bus clock. DDR3 is also sometimes called PC3-6400 for its peak transfer rate of 6,400MB per second. DDR3-800 differs from DDR2-800 only in the speed of its memory clock -- 100MHz vs. 200MHz -- and its cycle time -- 10 nanoseconds vs. 5 nanoseconds. As of 2011, this memory type is largely obsolete.


DDR3-1066, or PC3-8500, offers a 133MHz memory clock and 7 1/2-second cycle time, with a 533MHz I/O bus clock. This memory actually has a peak transfer rate of 8,533MB per second, rather than the 8,500 implied by its common name. This is due to the convention of rounding down decimals when figuring the data rate of memory.


DDR3-1333 memory offers a 166MHz memory clock and a cycle time of only 6 nanoseconds. The I/O bus clock runs at 667MHz. DDR 1333 is also known as PC3-10600, and may be sold this way by computer retailers, but actually provides a peak transfer rate of 10,667MB per second. Some manufacturers round this memory's capacity differently and may call it PC3-10666 or PC3-10700. However, these differences in marketing don't indicate any difference in memory speed or efficiency.


DDR3-1600 RAM offers 1,600 million data transfers per second and a peak transfer rate of 12,800MB per second. It has a 200MHz memory clock and a 5 nanosecond cycle time, with a 933MHz I/O bus clock. As of 2011, this RAM is the highest readily-available speed of DDR3, though faster RAM can be purchased through some speciality retailers.


Also called PC3-14400 and DDR3-1866, DDR3-1800 memory has a memory clock speed of 233MHz and a cycle time just over 4 nanoseconds. Its I/O bus clock is 933MHz. This memory offers 14,933MB per second as its peak transfer rate. Due to rounding differences, this RAM may also be called PC3-14900.

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