DDR2 667 = DDR2 800 on Conroe?

In a new article from the CPU magazine, Anand Lal Shimpi wrote a few interesting words.

Based on my testing, while DDR2-800 looks nice on paper, it’s simply not necessary to get the most performance out of your system. As long as you’ve got low-latency memory modules, DDR2-667 will perform just as well as DDR2-800. The explanation behind this is simple: Core 2’s FSB runs at 1,066MHz but is only 64 bits wide, delivering 8.53GBps of bandwidth to the CPU. Core 2’s memory subsystem is 128 bits wide but even at DDR2-667 can deliver 10.67GBps of bandwidth, meaning that unless its FSB frequency is faster than 1,333MHz, the CPU can’t use any more memory bandwidth.

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Provided thanks to Anand Lal Shimpi and CPU magazine.

I thought future upgraders might want to know this.

well if you overclock...like most of the people on this forum, then your FSB frequency will probably exceed that right?

Right, it's very easy to O/C 400 FSB with the lower end Core 2 Duo CPUs, so DDR2-800 is suddenly about the minimum you'll want... unless your DDR2-667 RAM will O/C to DDR2-800 speeds. If you plan on overclocking, get the faster RAM.

That is right, pretty much any FSB over 333 will allow you to use the DDR2 800 to it's fullest extent. The reason I posted this is because there are some people who read this forum who don't overclock, believe it or not.

if i'm using ddr2 667mhz memories and i dont' OC yet the FSBRAM ration is 4:5 does that mean my ram is runnign faster then the CPU?. shld i change its ration to 1:1 in the bios? but if i do won't it OC the CPU, which i dont want to do

batboy said:

Right, it's very easy to O/C 400 FSB with the lower end Core 2 Duo CPUs, so DDR2-800 is suddenly about the minimum you'll want... unless your DDR2-667 RAM will O/C to DDR2-800 speeds. If you plan on overclocking, get the faster RAM.

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And this is the reason I may pick up the deal @ Fry's for the 6400's slightly yummier multi and return my 6300...

behling said:

if i'm using ddr2 667mhz memories and i dont' OC yet the FSBRAM ration is 4:5 does that mean my ram is runnign faster then the CPU?. shld i change its ration to 1:1 in the bios? but if i do won't it OC the CPU, which i dont want to do

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The 4:5 ratio indeed means the RAM frequency is running 1.25X faster than the FSB. At default speed with a Conroe, the FSB is 266, so the RAM is running at 333 MHz or DDR2-667. That's exactly what your RAM is rated for. So, unless you are overclocking, just leave it at that setting. If you did change to the 1:1 ratio, that will not overclock the CPU unless you also change the FSB. If you used the 1:1 ratio, then you could O/C up to 333 FSB and still be in spec with your RAM. Of course, almost all RAM will O/C a bit higher than what it's rated at, especially with a bump in voltage.