RAM Mhz and compatability

[Klizzey]

Hey what's up guys, quick question. This mobo says that the memory it supports = 533MHz DDR2 , Dual Channel Supported , 667MHz DDR2 and 800MHz DDR2. When I run CPU-Z, it says my DRAM Frequencey is 333.5 MHz. I'm sort of confused because some posts i've read have said that 200 MHz is actually 400? Not quite sure how it works. Would my 333.5 MHZ frequency be considered 667 MHz DDR2 or 333 MHZ DDR2? Would like to know if the mobo will support my current Ram, thanks ahead of time :D

[skier]

the 333.5 Mhz being reported is what is called the FSB(Front Side Bus) which is half of the operating speed for RAM, so they are actually operating at 667MHz

(The FSB is kinda like a basic frequency to go by, it is the un-multiplied frequency(DDR(2) Ram has a x2 Multplier to achieve the operating frequency, and modern CPU's multipliers can range anywhere from x6-x14 or even higher))

this is a very simple crash course on FSB, enjoy

any more questions to help, feel free to ask

[Klizzey]

Very awesome! So my Ram would be fine with a motherboard that supports 667 MHz DDR2? Also, thanks a ton for the thorough and very quick reply.

[DMB2000uk]

the 333.5 Mhz being reported is what is called the FSB(Front Side Bus) which is half of the operating speed for RAM, so they are actually operating at 667MHz

(The FSB is kinda like a basic frequency to go by, it is the un-multiplied frequency(DDR(2) Ram has a x2 Multplier to achieve the operating frequency, and modern CPU's multipliers can range anywhere from x6-x14 or even higher))

this is a very simple crash course on FSB, enjoy

any more questions to help, feel free to ask

Don't want to crash in and say that's not what is going on skierkid, but can't help but clarify what you have tried to explain

Not all CPUs operate at 333Mhz FSB, so while right in the case of most core 2 duo's, it's not strictly true all of the time. RAM isn't always limited to running in sync (1:1) with the FSB so it's not just double the FSB speed. RAM's final frequency is actually calculated using FSB:RAM Mhz dividers, e.g. 3:2, 4:5 etc.

Ram that runs at 333Mhz is called 667Mhz RAM as it the RAM is Double Data Rate which means for every clock cycle it will be accessed twice. There aren't actually any multipliers that mess with it's 'base frequency'.

You are right in that FSB is like a reference frequency though

Sorry to have pulled your post to bits, but this way you can learn/remember the proper way it works and new members don't get any bad habits

Dan

[skier]

well, this i know, but i believe he wanted the simplest answer he could get, and notice "very simple," i certainly meant that, and for the majority, all one needs know is that most every system uses a 1:1 CPU:RAM FSB, can they differ, yes; but how often do they, not often, only if people have have maxed either the CPU or RAM, and want to OC the other even more(like when i used a 4:5 ratio to get my RAM to its potential in the AMD pc)

anyways, addressing the question at hand :

So my Ram would be fine with a motherboard that supports 667 MHz DDR2?

-Yes

[apaige]

This is why people (especially editors and BIOS developers) should always make the distinction between the memory clock frequency (166 MHz), the bus clock frequency (333.5 MHz) and the transfer speed (667 MT/s - that's Millions of Transfers per Second). The standard name (DDR2-667) refers to the transfer speed, while the module name (PC2-5300) refers to the transfer rate in megabytes per second (5,333 MB/s).
http://en.wikipedia.org/wiki/Front_side_bus
http://en.wikipedia.org/wiki/DDR2_SDRAM

[Klizzey]

Thanks guys, yah I just mainly wanted to know if my ram was consider the "677 MHz" type because that's what the motherboard supports. Looks like the answer is yes. Thanks :D