Why is my DDR3 1600mhz RAM running at 665.1 mhz?

[theone1989]

Sorry if this sounds stupid but it's the first time I've put together a computer.

I have 2 x 4gb of Corsair Vengeance DDR3 ram, rated at 1600mhz, it's paired with a i5-2500k processor (which is running at half the speed it's specified at) on a MSI GD65 motherboard running Windows 7 Ultimate.

On CPU Z it shows my memory is running at 665.1 mhz? Isn't that lower than even DDR2 ram? What's happening?

 

[skizzled]

You have to remember, DDR is double data rate. So, you'd take what CPU-Z shows and multiply it by 2 to get the current speed the memory is running at. Mine is 666.7MHz which is 1333.4MHz but I'm also using 1333MHz memory.

Check to make sure all the settings in the BIOS are set up correctly to match your kit as you should be seeing 800MHz in CPU-Z.

 

[ComputerManiac]

Just like Skizzled said set your RAM speed in BIOS to DDR3-1600. Then you will get your rated speed...

Have a nice day!

 

[theone1989]

You have to remember, DDR is double data rate. So, you'd take what CPU-Z shows and multiply it by 2 to get the current speed the memory is running at. Mine is 666.7MHz which is 1333.4MHz but I'm also using 1333MHz memory.

Check to make sure all the settings in the BIOS are set up correctly to match your kit as you should be seeing 800MHz in CPU-Z.

Thank you so much for that. I didnt realise.

I've set in the BIOS for XMP profile (auto). My ram now runs at 1600mhz with 796mhz showing in CPU Z.

 

[drescherjm]

The reason for this is on LGA1055/LGA1056 the maximum supported ram frequency is 1333 Mhz so the bios defaults to that. To overclock your ram controller (part of the cpu) you need to either set the speed or like you did use the XMP profile.