a question about overclock

Dell / XPS 630I
February 5, 2009 at 08:48:32
Specs: win vista 32bit, intel core 2 duo e4600
well this system has not had one problem or bluescreen yet since i overclocked it 2 months ago. the question is i was told before that if i overclock the fsb which i done back then to 1066 that i should put the mem to 533 but i have kept it at fsb 1066 and mem at 667 which is alot faster and i have had no problems whatsoever. why am i been constantly told to put the mem at 533 when using fsb 1066. thanks

overclock i have is multiplier 12x 3.2ghz was 2.4ghz
fsb 1066
mem 667
power 1.5.5 v

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February 5, 2009 at 10:05:43
The general recommendation for Intel systems (except the P4) is to run the CPU & RAM in sync at 1:1 ratio. And just to be clear, the ratio is in reference to frequency, NOT QDR or DDR numbers. 1066MHz FSB runs at 266MHz frequency, DDR2-533 runs at 266MHz frequency, so that is the ideal pairing.

To explain a little further, the CPU communicates with the northbridge chipset/memory controller via the FSB, & the northbridge chipset/memory controller communicates with the RAM via the memory bus. Optimal performance is achieved when both buses run at the same frequency. If one bus or the other is run at a different frequency (either higher or lower), it causes the northbridge to compensate for the difference & that introduces latency. And the introduction of latency (aka "wait-states") causes a decrease in performance.

However, there is a point where running the RAM bus faster than the FSB can counteract the latency. I've seen a few statements in forums that the ratio is 1:2, but I haven't found a reputable hardware site to backup that claim. So for a 1:2 ratio with the CPU at 1066MHz FSB (266MHz frequency), the RAM would be run as DDR2-1066 (533MHz frequency).

As for the P4, the netburst architecture was so inefficient that running the RAM bus faster than the FSB helped to mask the inefficiency. The usual recommendation for P4 systems is to run the ratio at 3:4 or 4:5, depending on configuration. For all other Intel systems (P1, P2, P3), 1:1 is the way to go.

Current AMD systems don't use a FSB so none of the above applies. But 1:1 is the way to go for all AMD systems prior to the A64.

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February 5, 2009 at 10:21:10
BTW, how did you determine that 1066MHz FSB (266MHz) with DDR2-667 (333MHz) is "alot faster"?

EDIT: one other thing...if you have DDR2-667 RAM & your motherboard is capable of 1333MHz FSB, why aren't you running the CPU at 3.167GHz (9.5 x 333MHz)? That definitely would be faster.

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February 5, 2009 at 16:48:13
quote: how did you determine that 1066MHz FSB (266MHz) with DDR2-667 (333MHz) is "alot faster"?
well for one i done alot of testing with the game crysis set at 1066 fsb and mem at 533 on the same level with the same resolution and ingame settings and at 533 mem it was slower than at 667 mem. i went back a couple of times and checked the differential between the 533 and 667 mem and 667 was running the game faster. i don't know any other way to explain it but it does. the smoothness of the game is better at 667 mem 1066 fsb 12x multi. @ 3.2ghz
im using ddr2 800mhz ram.
specifications on this memory is---
800 and 667-mhz ddr2 unbuffered sdram.
processor type---from the booklet
intel core 2 duo
intel core 2 quad
intel core 2 extreme(dual and quadcore)
at least 1mb cache
fsb speed 1066/1333 mhz. this is what the motherboard is capable of using for different processors.

why aren't you running the CPU at 3.167GHz (9.5 x 333MHz)? That definitely would be faster.
i tried so many time to run the multiplier at 9x and 9.5x with fsb at 1333mhz and mem at 667 and the pc would not post. i tried it alot of times. thanks

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