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FSB:DRAM ratio


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#1 genthore

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Posted 20 September 2009 - 10:02 PM

according to CPUZ my ratio is 1:2 FSB:DRAM

my memory is OCZ Platinum DDR2 800 Mhz
my Mobo is ASUS P5N E SLI which I believe is also 800Mhz FSB

why is that not 1:1 ratio and should /could I change anything to make things better

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#2 hamluis

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Posted 21 September 2009 - 08:44 AM

I'm going to attempt this...but bear in mind that I really don't know what I'm talking about, just trying to go through it logically :thumbsup:.

I suppose that I have to ask...what version of CPUZ are you running?

I just installed version 1.52 and I see no such stat...http://www.cpuid.com/cpuz.php. Perhaps you are using an older version of CPUZ and that particular statistic was removed from the newer version.

http://www.newegg.com/Product/Product.aspx...N82E16813131142

What CPU are you running? I believe that's a key item in this drill.

The FSB of the board is 1333/1066MHz. That is the range of "maximum effective bus speeds" which that board will support. That doesn't mean that the board cannot/will not do other speeds, but those are the highest ranges which the manufacturer of the board will take responsibility for.

From http://www.geekstogo.com/forum/How-to-overclock-t11177.html:

"CPU manufacturers have found ways to increase the effective speed of the FSB of a CPU. They simply send more instructions in every clock cycle. So instead of sending one instruction every one clock cycle, CPU manufacturers have found ways to send two instructions per clock cycle (AMD CPUs) or even four instructions per clock cycle (Intel CPUs). So, when you look at a CPU and see it's FSB speed, you must realize that it is not really running at that speed.

Intel CPUs are "quad pumped", meaning they send 4 instructions per clock cycle. This means that if you see an FSB of 800MHz, the underlying FSB speed is really only 200MHz, but it is sending 4 instructions per clock cycle so it achieves an effective speed of 800MHz.

The same logic can be applied to AMD CPUs, but they are only "double pumped", meaning they only send 2 instructions per clock cycle. So an FSB of 400MHz on an AMD CPU is comprised of an underlying 200MHz FSB sending 2 instructions per clock cycle."

So...your CPU bus speed is really X divided by 4...which gives an actual bus speed.

Since you are running RAM with a speed of 800, I have to guess that your CPU is running at either 200 (x2) or 400 (x2), depending on how you look at it.

So the question becomes (again)...what CPU is installed?

FWIW: Per CPUZ, the bus speed for my CPU (FX X2 4400) is listed as 200, while my DRAM (DDR2-PC5300/667) speed is listed as 328/333. Supported CPU speeds for my RAM modules are 200, 266, 333.

Worth reading, IMO: http://www.techsupportforum.com/hardware-s...tio-matter.html

Louis

Now that I have made a mess of things :flowers:, maybe someone more knowledgeable will try to enlighten both of us.

#3 genthore

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Posted 21 September 2009 - 03:01 PM

I thank you for the info- I knew there was some sort of multiples going on but wasnt sure.
I am not sure what the CPU has to do with the equation but I am currently using a Pentium D 940 3.20 nm65

is a 1:1 ratio better than a 1:2 ratio? is a 1:2 ratio good bad or just ok?

I have another post in this section that I am trying to work on that I thought might be related but I am starting to think that the memory FSB ratio is NOT the problem-
thanks again and if anybody else has any insight - please enlighten me.

#4 hamluis

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Posted 21 September 2009 - 03:09 PM

<<is a 1:1 ratio better than a 1:2 ratio? is a 1:2 ratio good bad or just ok?>>

What I gather...it all depends. That last link I posted covers that question...by persons who are much more understanding of the variables involved than I happen to be.

Louis

#5 genthore

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Posted 22 September 2009 - 04:54 PM

I did view the link but the guy only says that 1:2 would be better than the ratio he currently was using - he didnt really say if 1:2 was good or not.
Thanks for the reply - I did some more research and have all the info I need now.




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