Confused by memory speeds

[Bluelion]

Hi folks,

Could you clear this up for me please? I thought I had this straight, but after reading a few posts in this memory section, I see people recommending memory for FSB speeds which I don't understand.

I've borderline given up with the Q9450, too expensive, low multiplier vs SSE4 and 12Mb cache hmmm. Instead the low price and immediate availability of the Q6600 is very appealing right now.

If I get the Q6600 and the Asus Rampage Formula Intel X48 (which uses DDR2), I note that I can run a FSB of 400Mhz within mobo spec (1600). which with the 9x multiplier 3.6Ghz (the machine will be liquid custom cooled). Now this will be paired up with 8Gb ram, and this is where I'm coming a little unstuck. I would prefer to run a 1:1 ratio, as by my thinking should give the north bridge an easier time (is this correct or doesn't it really matter?).

Where I'm confused is by the memory speed. With a 400Mhz FSB and 1:1 divider, what in spec memory speed do I need? How does the "8000" in PC2-8000 equate say to a 400Mhz signal? I note that this speed ram is rated at 1000Mhz, which I can just about fathom is DDR (x2), DDR2 (x2), then another 2 for good measure to give the x8

As an aside, does anyone know of any isses with the 2x4Gb OCZ ReaperX PC2-8000 kits http://www.overclockers.co.uk/showproduct.php?prodid=MY-104-OC&groupid=701&catid=8&subcat=817 with the Asus rampage mobo? I'm after as fast a quad core/8Gb system as is economical to buy while retaining 100% reliability.

Thanks in advance for any responses.

 

[slowrunner]

400MHz FSB + 1:1 ratio = 800MHz @DDR2, which is bang on spec for PC2-6400 memory.

PC2-8000 memory is to put it simply, PC2-6400 that has been tested and proven to work at higher speeds. Therefore if it's rated at 1000MHz you could run it with an FSB:RAM ratio of 1:1 with an FSB of 500MHz.

 

[Tetras]

As said above you only need PC2-6400 to run in sync with a 400 FSB.

Intel FSB is quad pumped so the actual FSB for a 1066 FSB CPU is 266. To run in sync with that you need memory with an actual frequency of 266, which is DDR-533 (DDR is effective of double actual).

I would prefer to run a 1:1 ratio, as by my thinking should give the north bridge an easier time (is this correct or doesn't it really matter?).

Northbridge doesn't really care about running memory faster than FSB (though most prefer memory to be PC2-6400 or below but P35 can handle 1066 ok) but performance wise it wouldn't make sense, so it is smart to stick with 1:1 FSB-DRAM ratio.

 

[Admiral Huddy]

This may help you:

http://www.huddysworld.co.uk/Techpages/PCZone_TechieTalk_1.shtml

 

[Bluelion]

Thanks lads, I appreciate the time you took to answer me. The clouds of confusion are beginning to lift I'll take a long peruse through that link Admiral Huddy, thanks for that.