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About DDRII's work-frequncy

post #1 of 7
Thread Starter 
According to what I knew: 'DDR 400' & 'DDRII 800' have same core-clock-frequncy, 200mhz; and have different 'coefficient', similar to Intel-Cpu's "double pump" or "quad pump" the FSB.
With same core-clock-frequency and different coefficients, they get differrent work-frequency: 200*2=DDR 400, 200*4=DDRII 800.
So, it means DDRII 667's core-clock-frequency is only 667/4=166.

I know DDR's core-clock-frequncy lies on FSB and step on following FSB's rising. For example: When OC AMD 3000+'s FSB from 200 to 250, the DDR 400's work-frequency changes from 400 to 600.(suppose the MEM is able to obtain such a level)
My question is: Choosing DDRII 667 Instead of DDR 400 to fit PentiumD820, how much is the MEMORY's work-frequency when PentiumD820 is running on it's standard external colck ?
--Is the DDRII 667 working as 400=100*4), or 800=200*4)?
If the DDRII 667 unsupport such a high frequency, 800, It means I have to change the FSB:RAM ratio from 1:1 to other, like 200:166 ?

And,
Theoretically, when OC PentiumD820's FSB from 200 to 300, to aviod system down, what core-clock of RAM should I set? 100, 133, 166, 200..etc.
unsure, I guess it is the 100.

kowning that doing a test would be a better way to the answer, but I would rather to find it out first so that I can decide to whether buy them or not.
Sorry for my blunt English..

Best regards,
mebanna.
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post #2 of 7
Yhe ram you choose depends on what your mb supports. DDR and DDR2 ram will not run on the same mb.
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post #3 of 7
DDR2-800 is running at 400Mhz dual rate to make 800Mhz effective.
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post #4 of 7
Thread Starter 
Quote:
Originally Posted by busa
Yhe ram you choose depends on what your mb supports. DDR and DDR2 ram will not run on the same mb.
I'm sorry.
Doubtless, the way of my expressing is misapprehensive...
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post #5 of 7
Thread Starter 
Quote:
Originally Posted by pauldovi
DDR2-800 is running at 400Mhz dual rate to make 800Mhz effective.
Thank for the response.
Let me put this another way…

There are two PC:
1.AMD 3000+(200 standard external Frequncy, S-E-F) with DDR400,
2.PentiumD820(200 standard external Frequncy too) with DDRII667.

Under the 1st situation, MEMORY is able to synchro with CPU's S-E-F;
Under the 2nd situation, Memory is Not able to synchro with cpu's S-E-F because the FSB get 800mhz which is over loadong to Mermory's max burthen.

To avoid system down, what numerical value of MEMORY's frequency should be chosed to set, 166 or 133? (if they exist in CMOS' option)
And my point is: Is it true that FSB:RAM ratio can't be 1:1 whenPentiumD820 is running on standard external Frequncy with DDRII 667?

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mebanna.
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post #6 of 7
Quote:
Originally Posted by mebanna
Thank for the response.
Let me put this another way…

There are two PC:
1.AMD 3000+(200 standard external Frequncy, S-E-F) with DDR400,
2.PentiumD820(200 standard external Frequncy too) with DDRII800.

Under the 1st situation, when I overclock FSB MEMORY is able to synchro with CPU's S-E-F;
Under the 2nd situation, Memory is Not able to synchro with cpu's S-E-F because the FSB get 800mhz which is over loadong to Mermory's max burthen.

To avoid system down, what numerical value of MEMORY's frequency should be chosed to set, 166 or 133? (if they exist in CMOS' option)
And my point is: Is it true that FSB:RAM ratio can't be 1:1 whenPentiumD820 is running on standard external Frequncy with DDRII 667?

Best regards,
mebanna.
The computer's FSB has nothing to do with the memory rated clocks. If you buy a 820, then yes you DDR2-800Mhz will only run at 400Mhz. But if you overlock the FSB to 400Mhz, then the DDR2-800 will run at it full speed of 800Mhz.
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post #7 of 7
Thread Starter 
Quote:
Originally Posted by pauldovi
The computer's FSB has nothing to do with the memory rated clocks. If you buy a 820, then yes you DDR2-800Mhz will only run at 400Mhz. But if you overlock the FSB to 400Mhz, then the DDR2-800 will run at it full speed of 800Mhz.
Great ! I think that I see something now

"If you buy a 820, then yes you DDR2-800Mhz will only run at 400Mhz"
Do you mean that the memory rated clock is 200 so that it is synchro to cpu's standard external frequency(200) ?
So, if I replace DDRII800 by DDRII667, the DDRII 667 will only run at 400mhz, too ? and if I can overlock the FSB to 400mhz, to avoid system down, the DDR667 must be set to "100" instead of the original "166" in CMOS option ?

Thanks~
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