Help! How to sync OC'd RAM and CPU?! >.<

First off, I looked all over for the answer to this and read all the guides and FAQ's on these forums as well as others, but I'm still a little confused.

Basically, my question is: How do you sync OC'd RAM and Intel CPU's in terms of FSB and RAM speeds?

FSB, I don't quite understand how to tell what one's FSB is on their processor. I'm planning on buying a C2D E6600, at stock the cpu is at 240mhz FSB x 10 = 2.4ghz. But, looking at newegg/intel, the stock FSB is 1066mhz, wtf?! Which one is the FSB? Since Intel has 4 data transfers per clock cycle, is the real FSB 1066/4 = 266.5mhz?

The RAM. I'm planning on getting DDR2 800 RAM. Does the mean the actual clock speed on the RAM is 800/2 = 400mhz?

Should the FSB of the CPU match RAM speeds? 266.5mhz = 400mhz?

Moreover, say I overclocked my CPU to 400mhz x 10 = 4.0ghz. How do I need to overclock my RAM so that they run in-sync?

I realize how newbie all these questions must sound, I can only say that any help would be greatly appreciated. I hope to return the favor to another newbie someday. Thanks in advance to anyone who can help...

-Kuya

P.S. If I overclock my CPU to 4.0ghz, is the actual FSB 4,000mhz/4 = 1,000mhz... so I need to overclock my DDR2 800mhz RAM to 1,000mhz so they run in-sync? I'm so confused here... please help. >.>

Kuya said:

First off, I looked all over for the answer to this and read all the guides and FAQ's on these forums as well as others, but I'm still a little confused.

Basically, my question is: How do you sync OC'd RAM and Intel CPU's in terms of FSB and RAM speeds?

FSB, I don't quite understand how to tell what one's FSB is on their processor. I'm planning on buying a C2D E6600, at stock the cpu is at 240mhz FSB x 10 = 2.4ghz. But, looking at newegg/intel, the stock FSB is 1066mhz, wtf?! Which one is the FSB? Since Intel has 4 data transfers per clock cycle, is the real FSB 1066/4 = 266.5mhz?

The RAM. I'm planning on getting DDR2 800 RAM. Does the mean the actual clock speed on the RAM is 800/2 = 400mhz?

Should the FSB of the CPU match RAM speeds? 266.5mhz = 400mhz?

Moreover, say I overclocked my CPU to 400mhz x 10 = 4.0ghz. How do I need to overclock my RAM so that they run in-sync?

I realize how newbie all these questions must sound, I can only say that any help would be greatly appreciated. I hope to return the favor to another newbie someday. Thanks in advance to anyone who can help...

-Kuya

P.S. If I overclock my CPU to 4.0ghz, is the actual FSB 4,000mhz/4 = 1,000mhz... so I need to overclock my DDR2 800mhz RAM to 1,000mhz so they run in-sync? I'm so confused here... please help. >.>

Click to expand...

A stock E6600 runs at 266MHz x 9 = 2400MHz. 266MHz is base frequency that the CPU runs at, which is multiplied 9 times over to get 2400MHz. 266MHz is also the actual FSB frequency. Intel "quad pumps" their FSBs, which means that for this CPU the FSB runs at an "effective" rate of 1066MHz. The same goes for the other Conroes as well (E6300, E6400, E6700). They all run at 266MHz, the difference is the multiplier. 7 for E6300, 8 for E6400, 9 for E6600, 10 for E6700.

If you boosted the frequency from 266MHz up to 400MHz, this particular processor would thus be at 400MHz x 9 = 3600MHz. The FSB, because of being quad pumped, would be at 1600MHz.

As for the Memory, yes the DDR2 800 operates at a base frequency of 400MHz. It has an "effective" frequency of 800Mhz since the principle idea behind DDR (Double Data Rate) is that it uses both edges of the clock cycle (rising and falling) for data, rather than just one edge.


As for the memory/cpu sync, if I remember right (it's been awhile), the memory runs at whatever the FSB is set to. So even if you use DDR2 800 memory, it's going to run at 533 speeds if you leave the FSB at 266MHz. (266MHz x 2 = 533). If you boosted your FSB to 400MHz, the memory would be running at its native speed, if you indeed installed DDR2 800 memory.

Most everything is based from the FSB frequency, so multiply UP from that, rather than dividing DOWN from some overall speed.

Experts correct me on any of this if I'm wrong. Like I can't remember if Intels now have dividers to run the RAM and CPU at different speeds?

Wow... that already cleared up a lot of confusion. BIG THANKS to Sorin.

So to reach my 4ghz goal, I have to push my CPU 445mhz FSB x 9 = 4,005 mhz. This means I need to push my RAM to 890 mhz? (445x2 = 890)

Also, I've read there is a divider for Intels, will running my RAM faster than my CPU show any improvement in performance? ie. RAM at 1100mhz and CPU at 445mhz FSB?

Thanks again... I said it once before, I LOVE THESE FORUMS!!!

-Kuya

Kuya said:

So to reach my 4ghz goal, I have to push my CPU 445mhz FSB x 9 = 4,005 mhz. This means I need to push my RAM to 890 mhz? (445x2 = 890)

Click to expand...

Yes, exactly (basically, that is. you also need to raise the vcore when you overclock so that it will be stable). And if you do good research for the memory, it's not hard to get good DDR2 800 memory that will easily do 890.

Not that 4GHz is gauranteed of course, some E6600s will do better than others, which is true of any processor.

Kuya said:

Also, I've read there is a divider for Intels, will running my RAM faster than my CPU show any improvement in performance? ie. RAM at 1100mhz and CPU at 445mhz FSB?

Click to expand...

That I do not know, someone more versed in Intelese will have to chime in on that.

Thanks again Sorin. =)

so far as i know intel has dividers that can run the ram faster than the frontside bus. Therefore your system will default the ram to run at 400mhz while the fsb is 266. AMD will only allow dividers lower than the fsb (intel has these too of course)

Now as far as I know (not very intel knowledgeable) having your ram run at 1:1 (same speed as fsb) will give you the best bandwidth, because as the fsb reachs a clock to recieve data, the RAM bus is also at a clock to give it. I don't understand to dividers too much on the low level, but basically it gives less bandwidth because when the fsb becomes ready to receive the ram may not always be ready to give. Common sense tells me that this would apply for both higher and lower dividers. Anyway this is somthing you might have to experment with, because if you run the ram REALLY fast, it will definatly have a gain if its faster than the FSB. But remember you have another choice here anyway. If you ram can run fast you can use a lower multi on your cpu to achieve a high ram clock at 1:1.

Example. using what you give above you need 445mhz to run 4ghz on 9x. this means you ram will be at DDR890, but if you use 500fsb x 8 = 4000 you can run the ram at DDR1000 at 1:1 and get the best performance.

what cooling do you intend on using? if it isn't something subzero, then 4ghz is a VERY lofty goal. i wouldn't count on it on air (although you may get a screenshot). on air or water, 3.6ghz would be more likely.

pretty much everything posted so far is correct, except most mobo's don't allow running ram slower than fsb. so you are stuck with 1:1. you can run the memory faster than the fsb (ie 4:5, or 2:3, or 1:2), but it really doesn't help much, and sometimes the deviders can be buggy, holding back your oc overall.

Using water cooling, even so, I know 4ghz is a long shot, but its been done!

Pump: MCP355, w/Petra's top
Radiator: 120.3 Thermochill
Waterblock: Apogee

We'll see how it pans out. Also, I read somewhere that there is barrier to the FSB on intel chips... anyone know anything about this?