# Why is my DDR3 1333mhz RAM running at just above 667mhz?



## Rysuko (Jul 24, 2009)

I just finished putting together a new build.

Build: Antec 900 Case
Asus M4A78T-E Motherboard
Phenom II 955 BE CPU
6 GB G.Skill 1333mhz RAM
Zalman 9900 CPU Cooler
Acer X193W Monitor
Windows Vista 64.bit w/ free Windows 7 upgrade

All 6GB shows up, but the highest speed only goes to just 667mhz. The motherboard isn't even rated for running frequencies those low. The RAM is rated at 1333mhz so what's the deal? How can I put it at the speed it needs to be at?


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## manic (Aug 2, 2005)

667x2=1334 sounds about right. I get confused with ram, I could be
wrong, but it looks right to me.


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## Rysuko (Jul 24, 2009)

manic said:


> 667x2=1334 sounds about right. I get confused with ram, I could be
> wrong, but it looks right to me.


Good point, I think you're right. Thanks.


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## McNinja (Jun 22, 2008)

Can you post your memory with CPU-Z in the tab of SPD, please.
CPU-Z

My ram is 800mhz but it shows up as 400mhz since its DDR2. I have my ram in slots 2 and 4 since my giant Heatsink takes the first slot.


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## Rysuko (Jul 24, 2009)

Sure thing. Here is a screenshot for you.




Mcninjaguy said:


> Can you post your memory with CPU-Z in the tab of SPD, please.
> CPU-Z
> 
> My ram is 800mhz but it shows up as 400mhz since its DDR2. I have my ram in slots 2 and 4 since my giant Heatsink takes the first slot.


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## McNinja (Jun 22, 2008)

Yea your ram looks correct. It should be running at full speed. You can wait for other techs to give you more detailed response with JEDEC #'s but I see that is 10666 RAM and the last JEDEC or EPP is usually the indicator of the speed.


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## Wrench97 (May 10, 2008)

DDR = Double Data Rate, double the reading CPUz shows on the Mem tab because the ram reads and writes on the up and down pulse of the signal.


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## McNinja (Jun 22, 2008)

I see with your Ram its the JEDEC #1 that is the main frequency of the ram. It is 444mhz X 3 = 1332mhz. Hey Wrench how do you tell which of the frquencies give the actual rate and do they apply to all of the DDR3 sticks of RAM?


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## Wrench97 (May 10, 2008)

On the Mem tab lists the current speed, the SPD tad lists all available speeds.

This is off my laptop with 533mhz ram.


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## McNinja (Jun 22, 2008)

I found exactly what I was looking for.



> Adjusting the divider:
> Everyone uses archaic terms like set a 1:1 divider. Show me an AM2 motherboard with DDR2 memory that has a CPU:memory ratio option in the BIOS and I'll give you a cookie . As a noob learning to overclock a couple months ago I was like.... "huh?" everytime I heard someone say that, because I had no idea what they meant. I think when people say that, they're referring to the old 939 days where the reference clock was 200MHz (still is) AND the frequency of the memory was 200MHz (but 400MHz effectively since its DDR, or double data rate memory). So setting your memory to DDR 400 was setting it to operate at 200MHz just like the reference clock, or a 1:1 ratio. Those were the simple days when that's all you had to do. In today's world with DDR2 memory, the 1:1 ratio doesn't have much meaning.
> 
> Here's what effects the divider with DDR2 memory and AM2 sockets. The CPU multiplier, and what I call the "memory setting" (i.e. DDR2 800, 667, 533, 400). It's not really accurate to just say set the divider since two factors influence it, so several combinations will yield the same divider.
> ...


Memory Speeds explained

Ok Rsyko you should have a look at this too. I doesn't refer to DDR3 but its confusing enough.

I would have a look here 

Wiki on DDR3


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