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how to correctly match memory speed with FSB speed?

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April 11, 2008 12:09:34 PM

hello

is there a guide how to correctly match memory speed with FSB speed? and what is the advantage of the correct matching?

thanks

More about : correctly match memory speed fsb speed

April 11, 2008 12:32:51 PM

There's not very many benchmarks on the internet that show benefits of matching memory speeds to fsb.

It's widely believed that a system is more stable and will run better at a 1:1 ratio between FSB and Memory speed, but again, not much data to back it up.

Basically DDR2 speeds need to be divided by 2 to match up to FSB. In my case that means my DDR2-800 gets divided by 2 to get to 400Mhz. I have my FSB set to 400Mhz as well for a 1:1 ratio.
April 11, 2008 12:52:42 PM

yeap, it seems memory speed must be integer of FSB

so, I have to devide ddr2/3 speed by 2

and FSB? what value do I have to consider? FSB / number of cores? eg for a dual core 1333? and a quad core 1333?
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a b à CPUs
April 11, 2008 1:00:38 PM

CPU fsb is quadpumped, multiplied by 4, so 1333 equals true FSB of 333. so for 1:1 ratio you'll only need DDR2-667 for stock speeds.

edit the number of cores has nothing to do with it
a c 172 à CPUs
a b } Memory
April 11, 2008 1:53:22 PM

Gotta be careful of definitions.

The FSB (thing) is the group of PCB traces connecting Intel CPU's to the chipset.

The FSB (adjective phrase) frequency is the speed at which the FSB operates - 266 MHz, 333 MHz, or 400 MHz.

The FSB (adjective phrase) clock = FSB freq X 4 (quad-pumped - transferring four chunks of data each bus cycle). This is the coresponding 1066 MHz, 1333 MHz, or 1600 MHz.

I've noticed that most people tend to use "FSB" for all three and depend on context for meaning. Usually, it works.
a b à CPUs
April 11, 2008 2:22:52 PM

You don't match the FSB speed to the memory. You adjust your multiplier and your FSB for the fastest overclock. Like me, I'm running DDR2 800 memory. I have OC my E6600 to 3.29 Ghz. I'm at x 9, at 366. So my memory is running at 366 or twice that since it's DDR2. My CPU is at 3.29 (366 x 9). Ohh 1:1 ratio,

My CPU, Northbridge chip, memory, and/or motherboard won't allow me to go any higher even though it's decent OCZ ram rated at 800 (400).

So you don't match, you slowly adjust your bios settings upward with running tests like Memcheck, Orthos, etc to get to the max your system can handle. Some peeps have got their FSB to 500 with 800 ram by pumping voltages WAY up and relaxing ram timings (5-5-4-17 means ram timings)
April 12, 2008 2:43:19 AM

(corrected version)

The FSB (adjective phrase) clock = regularly varying timing signal which controls data transfer on FSB.

Intel "quad-pumped" FSB datarate = frequency of FSB clock * 4 (e.g. 1333MHz datarate for 333MHz clock)

a c 172 à CPUs
a b } Memory
April 12, 2008 7:35:59 PM

You have a point. If we are going to get picky, let's get really picky.

But my main point is true. Nearly everyone DOES have a tendency to use "FSB" generically.
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