Why is my DDR3-1333 ram running at DDR3-1066 speeds?

Question

I have an HP Pavilion DV7-4100 (Intel i5-460m). It's user guide specs show DDR3-1333 and it came with 2 sticks of it. However, several utilities show:

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Dram Frequency: 533mhz

Timing - 7-7-7-20

FSB - 133mhz (21 multi)

FSB:DRAM - 4:16

Memory - Crucial, 4096MB, DDR3-1333, CT51264BC1339.M16F

Aida, Sandra, Cpuz, & Cpu-tweaker all show benchmarks equivalent to DDR3-1066 speeds. (when I say speeds, I mean frequencies, GB/s, nanoseconds etc... all the tests)

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So, from my limited knowledge, my bus speed SHOULD be running at 166mhz. Cause then you would double it (since that's what DDR does) to 333. Which according to the FSB:DRAM ratio would bring it up to 1333 with a Dram frequency of 666. But since mine is 133, it equates to a DDR3-1066 speed. But if the bus speed was brought up to 166, then my CPU speed would be in the 3.4ghz range (which is NOT what the i5 460m is rated for). So, did HP lie about what the memory speed is, or am I missing something?

By the way, it has a crippled bios interface and there are no settings the user can change.

Answer 1

The speed of the FSB is goverened by the processor in the motherboard. The same motherboard may well be capable of supporting different processors with different FSBs. A faster processor with a 166MHz FSB will run the memory at DDR3-1333. The quoted specifications are what the motherboard (northbridge / southbridge chipset) is capable of, not what your specific computer is supposed to be performing at.

Answer 2

The memory itself is DDR-1333 memory, as advertised by HP, but it is effectively useless because of the processor that is in the laptop.

The memory is CT51264BC1339 which according to the specs page is

DDR3 PC3-10600 • CL=9 • Unbuffered • NON-ECC • DDR3-1333 • 1.5V • 512Meg x 64

But according to the Intel spec page for the i5-540m it only supports DDR-1066 memory

Memory Types DDR3-800/1066

So HP basically put overspecced memory in a laptop with a processor that cannot support the higher speeds of the memory.