FSB:DRAM 1:1 ratio question

HP Pavilion 750n
September 14, 2007 at 17:39:04
Specs: Vista Home Premium 32bit, E6850/PC2-6400
I've searched all over these forums and read that keeping your ram and FSB frequency on a 1:1 ratio is the best for performance. I understand this, but I don't understand however why, if keeping this on a 1:1 ratio is the best for performance, do motherboard makers keep producing boards that exceed this.

For instance, I have a Gigabyte GA-P35-DS3R, E6850 333FSB, and PC2-6400@400MHZ. This automatically gives me a ratio of 5:6 FSB:DRAM, so I had to set the memory in the bios to 667 to get it at a 1:1 ratio, effectively underclocking my ram. The board supports DDR2 800, and DDR2 1066 only. So, why then would anyone even think about using DDR2 1066 if that basically ruins the 1:1 ratio (assuming you're using a 333FSB cpu)? Even using DDR2 800, with a 333FSB cpu, still makes the ratio 5:6. I don't understand that part of it.

I would like to know if what I said is correct, because to reach the 1:1 FSB:DRAM ratio I had to underclock my ram and I would like to know if it's worth it.

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September 14, 2007 at 19:17:17
What you really should be asking is why are memory manufacturers producing RAM that far exceeds the FSB capabilities of current CPUs.

One advantage to underclocking high rated RAM is that you can usually tighten up on the timings significantly. If you have DDR2-1066 with default timings of 5-5-5-15 & clock it down to DDR2-677 to run in sync with a 1333MHz FSB CPU, you *may* be able to set the timings as tight as 3-3-3-8. Try to find DDR2-667 with default timings like that!

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September 14, 2007 at 19:29:11
"What you really should be asking is why are memory manufacturers producing RAM that far exceeds the FSB capabilities of current CPUs."

Yes, that's probably the better question.

So, does using a faster ram give any significant performance increases if it can't can't be run on a 1:1 ratio? Why then do they make DDR3, and to run something like that would you have to underclock it to match the FSB speed?

Also, does this mean I am getting better performance from my ram now that it's running at 667, at a FSB:DRAM 1:1 ratio, then it was before at 800, FSB:DRAM 5:6 ratio? So would that mean DDR2 1066 runs faster with a 333FSB CPU if it was set to 667, rather than 1066?

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September 28, 2007 at 08:52:44
The higher clocked the RAM is, the more performance one will get from the RAM. the 1:1 thing is a bunch of bull. Other devices besides the CPU request and store in RAM. Just look at any modern day video card and you will see the RAM clocked 2 or 3X higher than the GPU. Considering the bus of the P4 is quad pumped(4 signals per clock) compared to DDR, which is only at 100, 133, 166, or 200(double pumped, ie 100 = 200DDR) There is QUITE a bit of lag between the CPU and RAM. So PLEASE stop saying the 1:1 ratio BS around here. The faster the RAM, the faster the access time and the more data can be sent in and out. I am NOT trying to insult anyone here, but I am trying to stop the BS rumor from spreading any further!

Just run Sisoft Sandra at different RAM speeds and see how much more data one can pump through it. Or run any benchmark(3Dmark for example) with the different RAM settings, the higher the RAM clock, the higher the score.

So please STOP spreading this rumor.

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October 11, 2007 at 01:43:03
so u r saying higher clock ram is better even if the cpu is slower right

i have ddr1 ram real clock of this ram is 200mhz and effective or double is 400mhz
i have p4 processor real clock is 100mhz fsb is 400mhz
when i selected dram frequency 400mhz under bios my pc ddint start up and i heard beep noise if u r saying higher clock is better then y my pc ddint start this proved we need to run under sync cpu and ram both run under sync i mean
i selected dram frequncy 200mhz means the ram is running at 100mhz which is also my cpu real speed.so u r wrong ok

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