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G.SKILL DDR3 RAM Frequency

Last response: in Memory
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February 13, 2010 8:45:41 PM

Hi.

I have the ASUS Crosshair III motherboard on which I installed a pair of 2 GB DDR3 ram. I already knew that I needed to increase the frequency of my memory from the default value to 1600Mhz. So I did that and saved the configuration in the BIOS.

My problem is that when I check my stats on my PC, it shows 802 MHz. Is it normal because 802*2DIMMS = 1600MHz? If not, is there another way to change the frequency. Maybe a program like AMD Overdrive but for RAM ;) 

Another problem is the CAS Latency. It's supposed to be 9-9-9-24 but it shows 11-11-11-29.

Any solutions?

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a b } Memory
February 14, 2010 7:23:11 AM

Are the RAM modules rated to run at 1600 MHz at the default 1.5 volts? You may need to tweak those first before applying changes to the timings. If your modules say 9-9-9-24 @ 1.65V, then you need to set your DIMM voltage to 1.65 volts, and set the timings manually to 9-9-9-24.

As for the frequency, that is the nearest it can get to 800 while being an integral multiple of your processor's reference clock. (ie. if your processor's reference clock is 160 MHz, and you have DDR3-1333 MHz RAM, then your modules will most probably run at 1280 MHz because that is the nearest it can get to 1333 without going over significantly).

Finally, no. For DDR memory, you always multiply the frequency by 2 to get the "effective" frequency. In this case, the modules physically run at 802 MHz, but are running at 1604 MHz effectively because of the transmissions at the rising and falling end of the clock signal.
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February 14, 2010 3:40:06 PM

gracefully said:
Are the RAM modules rated to run at 1600 MHz at the default 1.5 volts? You may need to tweak those first before applying changes to the timings. If your modules say 9-9-9-24 @ 1.65V, then you need to set your DIMM voltage to 1.65 volts, and set the timings manually to 9-9-9-24.


I now set it to 1.5 V but my timings remain 11-11-11-29. I do not see any option for that in the BIOS, is there another way to change that?

gracefully said:
As for the frequency, that is the nearest it can get to 800 while being an integral multiple of your processor's reference clock. (ie. if your processor's reference clock is 160 MHz, and you have DDR3-1333 MHz RAM, then your modules will most probably run at 1280 MHz because that is the nearest it can get to 1333 without going over significantly).


How do you check the reference clock? Mine is the AMD Phenom II x4 955 BE
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

But what practical impact does that have on me? After all, it's only good to know but it's automatically done if I understand correctly.

gracefully said:
Finally, no. For DDR memory, you always multiply the frequency by 2 to get the "effective" frequency. In this case, the modules physically run at 802 MHz, but are running at 1604 MHz effectively because of the transmissions at the rising and falling end of the clock signal.


Oh, I understand now. So it seems my DRAM frequency is set up correctly.
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a b } Memory
February 15, 2010 8:34:19 AM

What are your RAM's specifications, to begin with? Can you post a link to your module? Are they rated to run at 1600 MHz?

I'm not very familiar with AMD, so I can't answer your question. Suffice to say, everything should be done automatically. Your processor is even a black edition, so multipliers can be set manually.
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February 17, 2010 1:51:24 AM

I searched a bit more in the manual and found that to change the timings manually some other settings had to be put on manual first in the BIOS which explains why I couldn't find it. All the information seems correct in CPU-Z now.

My memory is the one most would probably buy if they shopped for dual channel DDR3s on newegg:
http://www.newegg.ca/Product/Product.aspx?Item=N82E1682...

Do tell me about the reference clock though. Does it influence the things I personally have to set or is it just for 'its internal tweaking'?
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a b } Memory
February 17, 2010 9:11:04 AM

Okay, your RAM is indeed rated to run at 1600 MHz.

The reference clock is a sort of template for how fast everything runs. Your CPU bases its frequency on the reference clock, your RAM adjusts itself to be running at an integral ratio to the reference clock, etc etc.

We need an expert here. I can't explain this.
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February 23, 2010 11:34:26 PM

Best answer selected by paulhammerling.
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