DDR3 Buying (AMD Phenom II 955) Speed or Latency?

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HaGGardSmurf

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Oct 16, 2009
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It's time to upgrade my ram, I currently only have 4GB

My motherboard is an Asus M4A89GTD Pro which supports 4 x DIMM, Max. 16 GB, DDR3 2000(O.C.)/1333/1066 ECC,Non-ECC,Un-buffered Memory I also have a Phenom II 955

I have DDR3 1600 running at 1600 currently, so I know I can run that speed, and am sort of looking for 4 x 4GB at that same speed.

However that's why I am here, you guys are the experts so I dont know if I should look to buy that speed again, or if I should look for like CAS 7 at a lower speed, or what to do.

Please help guys :S

(Also, I'm in canada so I'll be buying from newegg.ca for example so please use that site or another .ca if your linking things as newegg.ca will not sell some things the us site does)
 
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C12Friedman
I was looking for the formula and found this, "...So you’ve figured out how much RAM you need, but how fast should it be? Well, for the best results, it should be as fast as your motherboard allows. This would be for anyone who wants to be on the bleeding edge of performance, like a hardcore gamer. The average consumer won’t have much need for the fastest RAM in the world, and that stuff can get pretty expensive. Instead, DDR3-1600 is a nice middle ground. It’s still fast, but not so fast that it costs a hefty premium.

But wait! Before you run down to the store and fork over all of your hard earned money for fastest rated RAM you can find, there’s one more thing to consider: Latency. Memory modules are also rated in “Timings,”...
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HaGGardSmurf

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When I was first building this PC, the research I did on ram at the time I found out that the differences in AMD and Intel cpu's as far as RAM is concerned is that Intel benefits from high clock speeds and AMD benefits from tight timings. Is that still the case?

Will I really see a difference if I bought a 7-7-7-24 setup vs a 7-9-8-24? If memory serves me the cas timings have to do with the number of clock cycles it takes for the ram to find the info. So wouldn't low + tight timings be good, or are we talking like a 5% difference real world?
 
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C12Friedman

C12Friedman

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Jan 25, 2012
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I was looking for the formula and found this, "...So you’ve figured out how much RAM you need, but how fast should it be? Well, for the best results, it should be as fast as your motherboard allows. This would be for anyone who wants to be on the bleeding edge of performance, like a hardcore gamer. The average consumer won’t have much need for the fastest RAM in the world, and that stuff can get pretty expensive. Instead, DDR3-1600 is a nice middle ground. It’s still fast, but not so fast that it costs a hefty premium.

But wait! Before you run down to the store and fork over all of your hard earned money for fastest rated RAM you can find, there’s one more thing to consider: Latency. Memory modules are also rated in “Timings,” generally a sequence of numbers, such as 9-9-9-24. The most useful of these is the first number known as the CAS Latency. This is the number of clock cycles it takes the RAM to access a column of data (the smaller the better), and in conjunction with the speed of the RAM, can be used to calculate its response time. The formula is

1000 * CAS
——————————
(RAM Speed ÷ 2)

This will give you the response time in nanoseconds. So for example, a certain DDR3-1866 module of Kingston HyperX memory has a CAS latency of 11 while G.Skill makes a DDR3-1600 module with a latency of just 6. The result? G.Skill’s slower RAM can respond in just 7.5ns where it takes the much faster HyperX RAM 11.7ns. This means that the G.Skill memory will be faster when it comes to random access; however, the higher clock speed of the HyperX memory still nets it more bandwidth, making it better suited for bulk operations.

Typically speaking, you want to settle on a clock speed first and then use CAS latencies to decide from there. Keep in mind that tighter timings mean more expensive. For instance, the difference between a CAS of 7 versus 8 is almost negligible." found here http://www.maximumpc.com/article/features/memory_buyers_guide_whats_best_ram_my_system?page=0,1

which sums it up better (at least as well with no effort) than I could
 
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