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Ram Bus Speeds

Last response: in Motherboards
December 16, 2010 4:12:51 PM

I was looking for components for a new build I'm planning and than noticed:
Many of the rams work at higher bus speeds than 1333 Mhz.Going over 4 gb,almost all kits are at 2000 Mhz speeds.However,the motherboards can support those speeds mostly only by overclock.(1333/1600/2000(O.C.)) means that,right?
Why is there such a gap?


More about : ram bus speeds

a c 108 V Motherboard
December 16, 2010 5:12:50 PM

Yes, "(O.C.)" means overclock. What you're seeing is not the bus speed of the RAM, but rather the frequency at which the RAM can operate. The reason is for overclocking. With quad (and now hex) core CPUs, data is sent 4 times per clock cycle. Some people opt for the RAM with higher frequencies so that they can OC their CPU w/o having to OC their RAM, and still achieve a 1:1 ratio.

For example:

If you overclocked your FSB to 1600, and had DDR2 800 (stock, no OC), you would have a 1:1 ratio. DDR is Double Data Rate, which is taking the bus speed and doubling it (400 MHz x 2).

Generally there is no big (if any) peformance gain with higher frequencies. RAM timings are far more important. The timing/latency describes how fast (in terms of clock cycles) data is transfered.

For example:

DDR3 2000 CL9 < DDR3 1600 CL8.
December 17, 2010 4:26:14 AM

Thank you.My concern is not performance gain though,it is compatibility.I'm no good at overclocking,but I want 6 gb of Ram and cannot find a kit under 2000 Mhz or a Mobo at 2000 Mhz...
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a b V Motherboard
December 17, 2010 4:37:23 PM

Ha, when I first saw the thread title the first thing that came to mind was that other Ram Bus . . .

Anyways, I'm not sure if the latency is quite that straight forward. From what I recall, it's basically the amount of clock cycles the ram takes to do its respective action. So, say, we're comparing 2000Mhz/CL9 and 1600MHz/CL8, we get 222.2 million operations a second vs 200 million operations a second, so 2000Mhz CL9 is still the victor by a bit. Of course there's a lot of different timings with the ram, but that's just in general.

I could be completely wrong on this count, I'm not sure.
December 18, 2010 4:54:49 AM

T_T said:
Just because you are seeing that the RAM and mobo support DDR3 2000, it doesn't mean that you have to use that frequency. The DDR3 2000 is the max that these components can handle. So, if the mobo you were interested in supports UP TO DDR3 2000, but the RAM you were interested in supports UP TO 1600, they are still compatible.


Oh,I see.So does it also work the other way?Meaning if the Mobo supports 1600 and rams are at 2000?
a c 108 V Motherboard
December 20, 2010 9:41:28 PM

Yes. In this example, if the mobo supported up to 1600, then your RAM (although supportive of up to 2000) could only be used to a max of 1600. As you can see, with the fluctuating costs of components, it is best to build your system based off of the mobo you intend to purchase. Everything else will be so much easier.