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Need Help Understanding My DDR3 RAM Settings

Last response: in Memory
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January 23, 2010 8:56:09 PM

I just built my first pc. Everything is running great with my new i5 750 build. I bought 4GB of g.skill ripjaws DDR3 RAM at 1600mhz. The CAS timings are 7-8-7-24-2N. Now I know with the i5 cpu you can't go any higher than 1333mhz or you'll lose the turbo feature unless I overclock (have not learned how to yet). I was able to go into the BIOS and change my CAS settings to reflect my RAM. I also changed it to 1333mhz. When I run CPUID and look at the memory tab I see my timings changed my the MHZ only reads 680 or something close to that. Where will I see the 1333mhz or how do I know my RAM is running at its best speed? I just want to make sure I'm doing everything right.

Thanks!

- manooly
January 24, 2010 2:10:53 AM

lol, I was about to post the same question. I don't understand that either.

Some help would be appreciated.

Nick

My memory: G-skill F3-12800CL9D-4GBRL X 2
AMD Phenom II X4 965BE @3.7Ghz
GIGABYTE 790FXTA UD5

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January 24, 2010 2:27:00 AM

OOps, should have read the FAQs first.

SPEED OF MY RAM
A: Under the memory section of CPU-Z you will find a text box labeled as 'Frequency'. This is the core speed of the module. Keep in mind for DDR the effective speed is double the core speed.

So, I guess that DDR3 doubles it too. So in my case: 802Mhz x 2 = 1600Mhz. The native clock of my sticks.

Must be the same for you Manooly.

You can check it out here http://www.tomshardware.com/forum/55024-30-memory-pleas...
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a b } Memory
January 24, 2010 3:28:40 AM

DDR stands for Double Data Rate. This means it transfers data on the rising and falling clock edges. The RAM manufacturers help to make this confusing because they want to repot high numbers. It doesn't necessarily matter what the numbers stand for, as long as they can report big ones.

So what you have is CPU-Z reporting the speed of the clock cycle, such as 800 MHz. But the RAM manufacturers double it - not entirely inaccurate because, remember, DDR stands for double[/] data rate - and call it 1600.

It's a case of the software and the memory companies calculating two different numbers. To translate between the two, double the DRAM frequency you are seeing in CPU-Z and that will give you the number quoted by the memory companies.
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