Are my RAMs really running at 800 MHz ?

[27MaD]

Hello guys , this question has been in my head for a really long time , my RAMs are 800 MHz , and my motherboard supports up to 667 MHz , so my RAMs are running at 667 MHz , but when i OC my CPU , i can see that RAM frequency passes 667 MHz ! , for example if i set FSB to 320 it says that RAM frequency is 800 MHz , even in CPU-Z it says DRAM frequency 400 MHz , how is this possible? i mean my board supports up to 667 MHz.

And btw the task manager says 667 MHz.

 

[cucker tarlson]

http://www.tomshardware.co.uk/answers/id-2103492/relationships-fsb-speed-ram-speed.html

download hwinfo64 and check the ram speed there,but if you've overclocked the fsb by 20% (266 to 320,1066 to 1280 effectively in qdr) your ram speed should increase by 20% (667 to 800). You can change it back to 667 by choosing a lower fsb to dram ratio.

 

[27MaD]

if you've overclocked the fsb by 20% (266 to 320,1066 to 1280 effectively in qdr) your ram speed should increase by 20% (667 to 800). You can change it back to 667 by choosing a lower fsb to dram ratio.

Yeah i know that but i thought my board can't give more than 667 MHz.

hwinfo says 400 MHz like CPU-Z.

 

[Shou Miko]

Yeah i know that but i thought my board can't give more than 667 MHz.

hwinfo says 400 MHz like CPU-Z.

U have to x2 that same goes for my DDR4 3000mhz ram, they run 1500.4MHz according to CPU-Z and in Bios 300MHz with X.M.P. Profile.

 

[Aquinus]

Yeah i know that but i thought my board can't give more than 667 MHz.

hwinfo says 400 MHz like CPU-Z.

The highest supported memory multiplier at stock is 667Mhz. When you overclock the base clock you're overclocking the input clock going into the memory controller (in your case the MCH.) At stock, the FSB is ~266.5Mhz so 667Mhz is had my multiplying the base clock. What you're seeing is the effective memory clock which is actually twice as fast as the actual clock since data is sent on both rising and falling edges of the memory clock. So your 667Mhz memory is actually running at 333.5Mhz (multiplied by 2 gets you your 667.) So, for your machine, the multiplier at 667Mhz is 5:4 (or 1.25.)

So 266.5Mhz * 5:4 = 333.1Mhz (which is 666.2Mhz effective.)
If you increase the core clock without altering the memory multiplier, the base clock changes but, the multiplier stays the same:
So 320Mhz * 5:4 = 400Mhz (which is 800Mhz effective.)

When the motherboard says it only supports 667Mhz memory, it means at stock settings with the highest supported memory multiplier. It says nothing about the core clock being bound to prevent changes to the memory clock. It's just that you can't use a multiplier higher than 5:4.

 

[27MaD]

The highest supported memory multiplier at stock is 667Mhz. When you overclock the base clock you're overclocking the input clock going into the memory controller (in your case the MCH.) At stock, the FSB is ~266.5Mhz so 667Mhz is had my multiplying the base clock. What you're seeing is the effective memory clock which is actually twice as fast as the actual clock since data is sent on both rising and falling edges of the memory clock. So your 667Mhz memory is actually running at 333.5Mhz (multiplied by 2 gets you your 667.) So, for your machine, the multiplier at 667Mhz is 5:4 (or 1.25.)

So 266.5Mhz * 5:4 = 333.1Mhz (which is 666.2Mhz effective.)
If you increase the core clock without altering the memory multiplier, the base clock changes but, the multiplier stays the same:
So 320Mhz * 5:4 = 400Mhz (which is 800Mhz effective.)

When the motherboard says it only supports 667Mhz memory, it means at stock settings with the highest supported memory multiplier. It says nothing about the core clock being bound to prevent changes to the memory clock. It's just that you can't use a multiplier higher than 5:4.

Thanks dude.