FSB and memory confusion!

[Mibs]

Hey guys, I've been researching a new build for a few weeks now and was set on the evga nforce 680i board, but I finally realized that I really don't need that board, so now I'm looking at the Asus P5KC. Anyway I've been reading so much lately that I now have myself utterly confused as far as FSB and memory is concerned. On this board you can't unlink the memory and cpu fsb. That is fine. Assuming I have an E6600 with a default 9x multiplier and of course a fsb of 266 and a pair of 1GB memory sticks rated for 800mhz here is what I have come to understand from my reading:

If I don't change the fsb then my cpu will be running at 2.4 GHz ( 266 x 9) and my memory will be running at 800MHz.

But then I started reading about overclocking the fsb and thought to myself..well if I change the fsb to 333 for example then I will have a 3 GHz cpu (333 x 9) but only 667 memory (333 x 2)? This is where I got confused. As you can probably tell from my incoherent post here it is late and I've taken in too much information in the past couple hours. It's 4AM here in Newfoundland and I'm just trying to get this straight.

So basically my question is:

If I leave everything at stock will my memory be running at 800MHz? Or will it go to 667 MHz by default since that would be the default fsb for the cpu?

Thanks for the clarification.

[cdn_Madrach]

Well Mibs.....I thought I had a handle on overclocking an intel but after reading your post I'm also CONFUSED now...Thanks...lol. Not sure about this answer but someone should be able to help shortly

[sswilson]

Originally Posted by Mibs

Hey guys, I've been researching a new build for a few weeks now and was set on the evga nforce 680i board, but I finally realized that I really don't need that board, so now I'm looking at the Asus P5KC. Anyway I've been reading so much lately that I now have myself utterly confused as far as FSB and memory is concerned. On this board you can't unlink the memory and cpu fsb. That is fine. Assuming I have an E6600 with a default 9x multiplier and of course a fsb of 266 and a pair of 1GB memory sticks rated for 800mhz here is what I have come to understand from my reading:

If I don't change the fsb then my cpu will be running at 2.4 GHz ( 266 x 9) and my memory will be running at 800MHz.

But then I started reading about overclocking the fsb and thought to myself..well if I change the fsb to 333 for example then I will have a 3 GHz cpu (333 x 9) but only 667 memory (333 x 2)? This is where I got confused. As you can probably tell from my incoherent post here it is late and I've taken in too much information in the past couple hours. It's 4AM here in Newfoundland and I'm just trying to get this straight.

So basically my question is:

If I leave everything at stock will my memory be running at 800MHz? Or will it go to 667 MHz by default since that would be the default fsb for the cpu?

Thanks for the clarification.

At stock CPU speeds, your memory will be able to run at it's rated speed as well.

It can get confusing because of the different FSBs that current intel chips run at, but to the user it's mainly hidden by use of memory dividers behind the scenes.

An example would be using DDR2 800 with a 1066 (4 X 266) proc.......

With the 266 chips, selecting a "memory speed (or type)" of DDR 533 (2 X 266) will automatically set a memory divider of 1:1 and memory will scale directly with changes to FSB.

If we want to use DDR2 800 with a 1066 (4 X 266) CPU, we set it for DDR 800 in Bios and the bios automatically sets a mem divider of (don't quote me on this... :) ) 2:3 with FSB being the two and mem speed being the three this gives us a memory speed of DDR 400 with a stock FSB of 266. With this setting, mem speed will scale faster than cpu speed as we raise FSB.

All that happens when we bring in a 1333 (4 X 333) FSB chip is that the mem dividers are changed to bring memory in line with the higher FSB.

With a 333 chip, your 1:1 ratio would be DDR2 667 (2 X 333) and your ratios for the other mem speeds will change to bring them in line at stock FSB.

Clear as mud???????

[3.0charlie]

yeah, thick mud.... and yes, it can get very confusing.

[sswilson]

Originally Posted by 3.0charlie

yeah, thick mud.... and yes, it can get very confusing.

Heh, it's hard to explain clearly other than to say that the bios automatically sets a divider based on what the stock FSB of your CPU is X what a person selects as installed memory speeds and thus arrives at the proper stock memory speeds.

Just to further muddy the waters.... most high end 1066 DDR2 is in fact just well binned DDR 667 or DDR 800 so the auto SPD settings don't pick it up for what it's supposed to run at.

OC'ing memory on the A64s was sooooooo much easier!!!!! :)

[3.0charlie]

I didn't mean when replying that your own reply was thick as mud... I meant that the whole process of oc'ing Mem can be "difficult" at times and is very difficult to explain clearly.

I've been oc'ing for 5 years, I would have a very hard time explaining Mem speeds to someone new in clear, concise terms.

I think you did your best, and re-reading your reply it does make sense.

John