Ram speed question

[LesPaul]

Sorry if this is a dumb question.. but i'm a little confused on what speed the RAM actually runs at.. lets say DDR 400 MHz for example. Ok, say your FSB is at 266 (133 x 2), does that mean your RAM is running @ 266 also, with the capability to be OC'd up to 400 MHz? Or does it run at 400 MHz reguardless of your FSB in asynchronous mode? I got a little confused on this when I read an article about running ram in asynchronous vs. synchronous, because I thought the ram ran at the speed of your FSB reguardless.

Thanks for any clarification you guys can provide.

 

[LesPaul]

anyone help a newbie out?

 

[NesuD]

Your ram actually runs at 133. The 266 figure is derived from the memorys ability to tranfer data 2 timed each clock cycle rather than once as in the past. For example of you were to have your cpu overclocked using a 200mhz cpu bus and the ram in sync with the cpu bus then your rams physical clock would also be 200 mhz but since the ram Is DDR it can transfer data 2 times each clock cycle rather than once each clock. Theoretically doubling it's data rate equal a 400mhz part of the old single data rate ram. Will it in reality be twice as fast? No but it is considerably faster than the old sdr ram. Your FSB isn't really running at 266 either It would only be 133 but there again it is a ddr bus so the cpu can trasfer data twice each clock rather than once on Athlon motherboards. I am sure you see how they are coming up with these numbers 266=133FSB 333=166FSB 400=200FSB.

P.S. Most of us who have been around here for a while think the only dumb question is the one you don't ask. Feel free to ask about anything you don't understand. The Anandtech Faqs are also a great place to learn things. many of them written by forum members go look them over and have a:beern me unless of course you aren't yet 21 in which case let me buy you a lemonade instead.

 

[LesPaul]

Thanks for the reply. I understand DDR technology, but what I'm confused on is how the FSB and the speed of the RAM are related. Is the speed of the RAM and the FSB two seperate clock speeds (ie. 133 MHz FSB clock and 200 MHz ram clock)? Or does the FSB determine what speed the RAM runs at (ie. 133 MHz FSB clock = 133 MHz ram clock)? For example, if you have RAM that is rated for a 200 MHz clock and your FSB is 133 MHz.. is the RAM going at 133 MHz with the potential for your FSB to be OC'd up to 200 MHz? Or, does the RAM run at 200MHz reguardless of your FSB speed, which is running at 133 MHz?

I hope this makes sense

Thanks,
LesPaul