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RAM... Frequency vs Latency

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March 30, 2010 5:35:24 PM

I am trying to decide on components for my first homemade PC. Built around the Phenom 550, I’m going try my luck at unlocking cores, but whether I can or not I intend to have a go at overclocking and hopefully learn something along the way.

This is what I am planning to build...

MB: M4A79XTD Evo - http://www.ebuyer.com/product/172846
CPU: Phenom 550 BE - http://www.ebuyer.com/product/166518
Graphics: Sapphire HD5750 512MB - http://www.ebuyer.com/product/179465
PSU: Corsair XT 650W - http://www.ebuyer.com/product/135514
This will be teamed with my existing Black Caviar HDDs, DVD drives, etc, and connected to my 1366x768 LCD TV.

I’m stumped by the choice of RAM though (I’m looking for 2x2GB).

My understanding is that the FSB and RAM operate best with a 1:1 speed ratio, which would equate to a RAM frequency double that of the FSB(?). So in my mind that suggests that the RAM need not be any faster than twice the highest FSB speed likely to be achieved through OCing.

I was further confused when I read (I forget where) that latency figures are more important than speed... the example I scribbled down said that 1333MHz 7-7-7-20 is better than 1600MHz 8-8-8-24.

Does this mean I should find the lowest latency RAM I can afford (on the Asus compatibility list) then check that the quoted speed is at least twice the FSB? Then whatever the difference between 2xFSB and RAM is my effectively FSB OCing potential without OCing the RAM?

So... how far off am I?! Any help gratefully received.

More about : ram frequency latency

March 31, 2010 1:02:35 AM

I don't exactly know, but I was under the impression that FSB RAM ratio thing only really applied to Intel Core 2 Duos and Quads.
So I'd just get the best RAM you can that isn't stupidly expensive - over £110. And you don't have to follow the Asus compatibility list, those are just the modules that have been tested, it certainly does not mean that other, untested modules, won't work.
The difference between 1333 7-7-7-20 and 1600 8-8-8-24 won't be noticeable outside benchmarks.

Even with lots of overclocking or with two of those graphics cards, your system won't use much power. Unless you want to be able to have a wider choice of hardware that you can put into that build then you could easily do it on a good 550W PSU.
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March 31, 2010 5:38:40 PM

Thanks guys... appreciated.

I've decided to go for Kingston HyperX 1333 CL7 available for £85-£100. I'm looking into better quality slightly lower powered PSUs too.

Cheers again

March 31, 2010 5:43:38 PM

I recommend replacing that 550 BE with the 555 BE. I unlocked mine with a GA-790XTA-UD4 (great mobo BTW) and its comparable to a 955 or 965 in terms of gaming. I have read that the 550's aren't unlocking as well as the 555 C3's.

Good luck!
April 1, 2010 6:44:50 AM

I'll have a look into that... thanks!

!