Big difference between 800MHz FSB and 667MHz?

[Link3978]

Would 800MHz FSB be considered a big difference from a 667MHz FSB? I am new to computer hardware so I am hoping that this is a straight forward question.

Edit: Maybe I should of put this in the motherboard section ...

 

[MU_Engineer]

Depends on the chip. What chip are you talking about?

 

[Link3978]

Well ... the merom. So if it depends on the chip guess this question can't be answered yet huh.

 

[MU_Engineer]

I assumed it was the Merom vs. the Yonah and not you hoping to bump the FSB on a 667 Dempsey Xeon to 800 to get better performance. The difference between the Yonah and Merom clock-for-clock is supposed to be about 10%. The 800 FSB on the Merom is because the Merom core needs more bandwidth than Yonah does.

I hope that answered your question. If you are asking how a Merom on a 667 FSB would do, my guess is that the lower-clocked ones would be okay but the higher-clocked ones would have a memory bandwidth bottleneck. We don't know that one because Meroms have not shipped yet. I'd like to know that one myself as a Merom on 667 MHZ FSB is half of a Kentsfield quad-core MCM and would be a good predictor of if Kentsfield would be FSB choked.

 

[Link3978]

Ohhh. So if I understand this right .... how bottlenecked the processor is by the FSB is what will determine how much of a difference a jump to 800MHz will be from 667MHz. So if a review of different models of the merom show the performace between them not being so great with the higher clock speed ones ... that maybe because the 667MHz FSB is bottlenecking it? And thanks for the response.

 

[1Tanker]

I assumed it was the Merom vs. the Yonah and not you hoping to bump the FSB on a 667 Dempsey Xeon to 800 to get better performance. The difference between the Yonah and Merom clock-for-clock is supposed to be about 10%. The 800 FSB on the Merom is because the Merom core needs more bandwidth than Yonah does.

I hope that answered your question. If you are asking how a Merom on a 667 FSB would do, my guess is that the lower-clocked ones would be okay but the higher-clocked ones would have a memory bandwidth bottleneck. We don't know that one because Meroms have not shipped yet. I'd like to know that one myself as a Merom on 667 MHZ FSB is half of a Kentsfield quad-core MCM and would be a good predictor of if Kentsfield would be FSB choked.

I guess you didn't see Anandtech's Yonah vs Merom comparo?

http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2808

It's still hard to pinpoint what affect the higher FSB has, as Merom also has 4MB L2 vs Yonah's 2MB.