Explain me this..

[allstars]

I´ve had over the past years oc´ed a few computers with Intel cpu´s.

Last oc was made with an Intel E6600 and its due to this my question goes.

What i´ve done was, i downgraded my memory modules to 533 (DDR2-800 original) to get the well known 1:1 ratio. Then i started bumping up the fsb, slowly.

The system now runs an impressingly 3511 MHz and its working perfect under all kinda tests, still with ratio 1:1.

Now.. My question is. Why is it the 533 number i focus at. The cpu runs 1066MHz at FSB according to manual, so i dont understand why i must go from 533 at baselevel before bumping the FSB.

Hope the question can be replied fast, since i write a school-project about clocking this cpu.

Thx in advance



/stars

 

[Regs]

double data rate. 533 x 2 = 1066mhz.

http://en.wikipedia.org/wiki/Double_data_rate

 

[allstars]

Yes, that i agree with. But do that then mean, that my memory DDR2-800 actually runs 1600 mhz ?

Or how do i explain my teacher, WHY i downgrade my memory to 533mhz.

 

[BitByBit]

Originally posted by: allstars
Now.. My question is. Why is it the 533 number i focus at. The cpu runs 1066MHz at FSB according to manual, so i dont understand why i must go from 533 at baselevel before bumping the FSB.

The FSB runs at a real frequency of 266MHz, but can provide the same bandwidth as a 1066MHz FSB, due to its ability to transmit data four times per cycle. Your memory runs at an external frequency of 266MHz, but can transmit data twice per cycle (DDR) hence its '533' rating.
So at those frequencies, your memory and FSB are indeed running at a 1:1 ratio.

Yes, that i agree with. But do that then mean, that my memory DDR2-800 actually runs 1600 mhz ?

Or how do i explain my teacher, WHY i downgrade my memory to 533mhz.

No. As inferred above, your memory runs at an external frequency of half its rating, in this case 400MHz. With DDR2, the internal clock runs at half the external clock (200MHz in this case), which is the reason for DDR2's increased latency over DDR. Regarding underclocking your memory to 533MHz, it is usual practice to do so when overclocking simply because it allows you to push the FSB further without pushing your memory beyond its limits. If you leave it at 800 and overclock your FSB by say 33%, your memory will now be running at 533MHz (1066MHz effective) instead of 355MHz, and is more likely to be unstable.

 

[allstars]

Cool..

You rock bigtime.. Thx a lot.

As usual, i get a lot of help and expertise from this forum.



Forza anandtech..



//stars

 

[MarcVenice]

I'm still wondering how this affects performance though. The memory supplies the cpu with data, no? So if the memory bandwith exeeds the amount of data a cpu can handle, it no longer is of any use, the extra bandwith, or is it ? Maybe I'm simplifying to much, but thats why I'm asking.

 

[orion23]

Well, synthetic benchmarks benefit from extra bandwith, other than that, the performance difference isn't that great.

The good thing about getting faster memory like DDR2 1000mhz, is that when overclocking, one would know that the memory alone will be able to handle @ the very least, a 500 FSB.