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Help me understand relationship between CPU and RAM while overclocking

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a b K Overclocking
November 10, 2011 12:16:34 PM

I recently built a system with a gigabyte ex58-usb3 motherboard, i7920, 12GB DDR3 1333MHz triple channel RAM. At stock CPU speed of 2.66 GHz my RAM only showed a speed of 1066MHz in the POST. When I manually changed the RAM settings to get 1333MHz, I would get occasional random restarts with an error stating that overclocking has caused system instabillity. I used the smart6 program provided by Gigabyte to OC CPU to 3.36GHz which also changed the RAM speed to 1280MHz. Do you have to maintain the same BLK with the Ram and CPU for stability? My motherboard supports 1333MHz and 2200MHz Ram and I was thinking about upgrading to faster RAM. If I do, will it simply default to 1280MHz to match the CPU and will it be better to simply get a faster CPU instead of faster RAM? If I do upgrade to a faster CPU will I need to get faster RAM also??


Thanks
Al
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a b K Overclocking
November 10, 2011 12:33:51 PM

Hi alrobishoud,

The BCLK frequency affects the memory speed (and also PCIe speed if I'm not mistaken) So, if you are increasing your BCLK you will have to decrease your RAM frequency to be stable at the same voltage.

Also make sure your ram is at the rated voltage. (Most tripple channel sets have a default of 1.65) if your RAM doesn't have the proper volts applied, you will be unstable.

Also make sure your timings are correct. If you tighten up your timings, you won't be able to run at a higher frequency.

If you are worried about your RAM, Set the BCLK back to default, Manually set all your memory settings to factory recommended (frequency, timings and voltage) and run memtest for a few hours
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a b à CPUs
November 10, 2011 12:54:25 PM

You should look in the bios at the ram speeds. You may need to set them manually to the spec on thier packaging to get the rated speeds of 1333 or 1600.

Often times the bios has an over clock menu, with an option to unlock or unlink the PCI-e and ram freq. This will give you the option to lock the pci-e a 100 where it should be and then overclock the ram and cpu any way you want, with out them messing with each other.

In my experience overlcocking with software in windows always leads to instibility.
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a b K Overclocking
November 10, 2011 1:57:21 PM

Thanks. The system only became unstable when I a manually changed the memory mulitplier from 8 to 10 with a frequency of 133MHz. When I let the software change the BIOS settings it changed the frequency to 160 with a multiplier of 8 for a total of 1280MHz for the RAM and it changed the CPU frequency to 160MHz from 133MHz with a muliplier of 21 for a total of 3.36GHz. I was not aware that the softeware may also change the PCI-e frequency as well. I will check that when I get home from work. The latencies and voltages did not change from what the default BIOS settings were which do match the manufacturers specs. I just noticed that the system became stable when I let the software make the changes which matched the frequency of the RAM and CPU to 160MHz. So I guess what I am wondering is does the base frequency of the RAM and CPU need to be the same for the system to be stable?
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a b à CPUs
a b K Overclocking
November 10, 2011 4:10:05 PM

You should learn to overclock manually, it is better and more rewarding. You should literally only need to change 4 to 5 settings for a mild to moderate overclock to around 3.5ghz.

1)Before overclocking set your ram to the lowest setting, that way it wont run out of spec.

2)Set uncore frequency to double that of your ram frequency, and make sure it stays like that after you raise the bclk.

3)set the ram voltage and timing to manufacturers spec.

4)This is optional for moderate overclocks, but I would set cpu voltage manually as well. This will take some experimenting. Best place to start, is too leave the computer stock. Load up cpu-z, and run prime95. Then set your voltage until the manually set voltage in cpu-z, matches what auto set. You then basically raise the BCLK and test for errors. You then can back the blck down, or up the voltage, rinse and repeat.

5)I personally would set the lowest qpi/link speed, that will help with stability. If all else fails, you can manually set qpi/dram voltage manually. Stock is usually 1.2v, and your plenty safe to around 1.35 and many go higher without problems.
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a b K Overclocking
November 10, 2011 4:20:40 PM

Thanks. I will give it a try. :) 
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a b K Overclocking
November 17, 2011 9:41:49 AM

Best answer selected by alrobichaud.
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