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Figuring out right ram for given cpu???

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Hey guys, new to the forum here. So i have a few questions about deciding what kind of ram to get based on the processor i have.

so i have a core 2 quad q6600 at 1066mhz
i understand that the cpu is quadpumped so its 266mhz*4
i have 2 gigs of ddr2-800, which means, if i understand it correctly, since its ddr, i have 400mhz*2 per stick. so with two sticks i exceed the 1066 and am limited by that throughput?

if someone could explain or send me a link to a thorough explanation of exactly how this works, i would appreciate it greatly. what i would like to know is how, given a fsb speed like 1066mhz, do i figure out what kind and how much ram i need to get a 1:1 ratio.

One more question dealing with something else: i'm getting an asus mobo that has ati crossfire technology and and intel north bridge but i have an nvidia card, can an nvidia card take advantage of the ati crossfire technology? and should i go for a similar mobo with an nvidia north bridge?

thanks so much guys.

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CPUs Master
Motherboard Master

Don't worry about the memory ratio; it really isn't that important with your Q6600. You could run the memory at 667 MHz, but it would be slightly slower or buy memory certified to work at 1066 MHz and gain up to 1 % performance (and possibly stability issues because the memory would be overclocked and require more voltage).

Quote:
i'm getting an asus mobo that has ati crossfire technology and and intel north bridge but i have an nvidia
card, can an nvidia card take advantage of the ati crossfire technology?
No.

Quote:
and should i go for a similar mobo with an nvidia north bridge?
Your options will be far more limited and NVidia based motherboards are not necessarily the most stable.

ok cool, that definately answered most of my questions--thanks. i am still uncertain about one thing regarding the cpu and ram. so if the fbs is 1066, should i use 1066 ram? from what ive read, 800 ram is more than enough to get the 1:1 ratio. can someone explain or send me a link to an explanation of why that is? i'd like to know the math you guys go through to calculate what kind of ram is sufficient to meet (not necessarily exceed) the throughput. i mean, i understand that ultimately we're limited by the fsb speed, so how do we get the ram to work most efficiently with the cpu? i just want to understand this more than anything. thanks guys.
CPUs Master
Motherboard Master

Since you already understand that the base clock is 267 MHz and assuming a non-overclocked Q6600, a FSB:D RAM ratio of 1:1 requires DDR2-533 MHz. 1066 MHz RAM allows a 1:2 ratio and 800 MHz RAM a 2:3 ratio. In other words, using a FSB:D RAM ratio of 1:1 doesn't mean that the system will be faster.
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thanks guys this was very helpful! i have one mroe question, just about ram though since im looking to get 2 more sticks. so i have right now 2x1gb ddr2-800 at 5-5-5-15, should i get 2x1gb ddr-800 at the same timings? or can i get them at lower timings? also, you can change their timings in the bios if the ram can be OC'd (that is if it has a voltage range)?
CPUs Master
Motherboard Master

It depends on the motherboard. If yours is picky with memory, then get identical RAM. You could get RAM with lower timings as long as it runs at the timings and voltage of the currently installed RAM. Overclocking RAM is not recommended if stability is important to you and the performance increase isn't worth the hassles (more voltage, heat, looser timings, etc.)

Buying RAM with lower timings and voltage like G.Skill PI Black DDR2-800 can make your life easier (I run 8 GB of G.Skill memory at 4-4-4-12 and 1.9V in a couple systems and they are very stable). DDR2-800 RAM allows you to overclock the FSB to 400 MHz and achieve the ideal 1:1 ratio.

thanks ghis. always very helpful as usual. i've learned a lot from just this one thread and you guys respond so quickly, its great! so if i can continue to be annoying with one final decision making question. my mobo broke down on me and im considering two different ones for its replacing. im at the point where i just dont know which one will be better, so im wondering if you guys will make it easy for me by making the decision lol. here are the two:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

i have an nvidia card so the crossfire tech isnt particularly useful. ill be running 4 gigs of ddr2 800 (different brands but both at the same timings and speeds) and ill be keeping my old harddrive which i think runs at 7200 rpm and like i said above ill have a q6600. thanks again guys :)  :)  :) 
CPUs Master
Motherboard Master

I own both motherboards and they work well with a Q6600. Here's what I can say about them:

- The GA-EP45-UD3P is less picky with memory and it has a better layout if you'll install several SATA drives. I use it for my Windows 2008 Server.
- The P5Q Deluxe has a slightly better on-board sound solution and it has Express Gate which is a nice toy, but not very useful once the OS is installed and working. Unlike the Gigabyte, it isn't 100% stable with G.Skill PI Black at 1.8V, but it's fine at 1.9V. Overall the Gigabyte is slightly more stable.
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