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Why did memory automaticall go from 5-5-5-15 to 5-6-6-16?

i have an e6750 that i am oc'ing on my gigabyte p35-ds3 board. it was 3.2ghz stable without changing the voltage, but i heard 3.4 was approachable without changing the voltage. i just went up to 3.3 and when i booted up, cpu-z says my g.skill pc2-6400 is 412.6mhz and 5-6-6-16...although it's rated at 400mhz 5-5-5-15 (which was perfect for a 3.2ghz oc). what does this mean exactly? should i go back to 3.2?
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  1. Best answer
    Most likely your mothboard had to relax your memory timings in order to OC the ram to keep up with the FSB. In case you don't know the math

    Speed = multiplier x (FSB/4) on core 2 chips (e6750 has a 8x multiplier)

    so at 3.2 Ghz you had a 1600mhz FSB which was perfect for you ram 400 x 2 for being double data rate then x 2 again for being dual channel gives you 1600mhz for memory band width. I would keep it at 3.2 personally.

    at 3.3ghz the fsb will be 1650mhz so to keep the ideal 1:1 ratio between ram and fsb the system oc'ed the ram.
  2. Best answer selected by tuffluck.
  3. PsyKhiqZero said:
    Most likely your mothboard had to relax your memory timings in order to OC the ram to keep up with the FSB. In case you don't know the math

    Speed = multiplier x (FSB/4) on core 2 chips (e6750 has a 8x multiplier)

    so at 3.2 Ghz you had a 1600mhz FSB which was perfect for you ram 400 x 2 for being double data rate then x 2 again for being dual channel gives you 1600mhz for memory band width. I would keep it at 3.2 personally.

    at 3.3ghz the fsb will be 1650mhz so to keep the ideal 1:1 ratio between ram and fsb the system oc'ed the ram.


    thanks. i understood the math as far as the 1:1 ratio and cpu fsb works and did also agree 3.2 was perfect since that puts the ram exactly where it is rated, however i wanted to push the cpu and just see what it could do on stock voltage (3.2 is an OC without changing the vcore). unfortunately 3.3 failed prime95 so i imagine i needed to up the voltage. in the end i agreed with you and that upping the voltage and increasing the timing of the ram wasn't really what i wanted to do for just the little extra bit of power. so, 3.2 it is. still not a bad OC on that chip (20%), especially with stock voltage.
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