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FSB speeds on Sandy Bridge

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January 19, 2011 5:48:16 PM

Hi,
I remember in old mobos there was an FSB, a channel connecting Ram memory with CPU via north bridge. For better optimization, it was important to keep the ratio of memory speed and FSB speed 1:1. I understand, that in new Sandy Bridge CPUs, the memory controller is built in. When I look at 2600K specifications, I see it supports up 2 1333MHz RAM memory.
Does this mean that the new "FSB" channel (I don't know how the new memory bus is called) is 1333 MHz? If it is so, is it possible to change its speeds to be compatible with higher speeds RAM memory?
a b } Memory
January 19, 2011 6:04:21 PM

The 1333MHz memory speed just means that that the maximum stock memory multiplier that would be used is 66.6 X 100MHz bclck = 667MHz * Double Data Rate = 1333MHz effective memory speed. If you have the right motherboard and CPU you can set the memory multiplier higher. Because the memory controller is fully integrated into the CPU die there is no internal bus that would cap memory speeds like the FSB would.
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January 19, 2011 6:29:53 PM

jprahman said:
The 1333MHz memory speed just means that that the maximum stock memory multiplier that would be used is 66.6 X 100MHz bclck = 667MHz * Double Data Rate = 1333MHz effective memory speed. If you have the right motherboard and CPU you can set the memory multiplier higher. Because the memory controller is fully integrated into the CPU die there is no internal bus that would cap memory speeds like the FSB would.


So basically in the new SandyBridge, the memory module and the memory bus are always running at the same speed (they one and the same)?
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a b } Memory
January 19, 2011 8:21:02 PM

The internal buses should be running at the same speed as the memory. I don't even think the BIOS gives you access to the speeds of those buses because they're part of the low level CPU design and hidden from the end user.
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a b } Memory
January 19, 2011 8:35:37 PM

It's now called BCLK. In the 1156 / 1366 series an increase in BCLK affected memory .... for example if ya increased ya BCLK from 133 to 167, ya memory speed (with the same memory multiplier of 8) went from 1066 to 1333 MHz .... go to a BCLK of 200 and it went to 1600 MHz.

SB is extremely resistant to BCLK adjustments .... most can't get past 103 ....saw one review site that got to 107.5

These guys think that someday peeps will be able to get to 115 .... I have my doubts .... but they explain the math so to speak.

http://www.guru3d.com/article/asus-sabertooth-p67-tuf-r...
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a b } Memory
January 19, 2011 8:45:55 PM

I was talking about the bus that transfers data, not the clock that controls all other frequencies. With the FSB on previous LGA775 you can actually tune the frequency of that bus separately from the memory speed, sort of, but now the details of the buses transferring data from the memory controller to the rest of the CPU are hidden and aren't adjustable, aside from BCLK changes which affect the entire system.
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January 20, 2011 4:31:36 AM

Ok, Iunderstand now. Thanks for all replies.
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January 20, 2011 4:34:35 AM

Best answer selected by Archimag.
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