The Move to DDR3: You Can Do It

The Phenom II 955 and 945 support both DDR3 and DDR2 memory. Just a couple of months ago you could save a good amount of money by going with DDR2 over DDR3, but these days the price difference is negligible.

A good pair of 2GB DDR2-1066 sticks will set you back around $57 while a pair of 2GB DDR3-1333 modules will sell for around $60. The problem is that faster DDR3 modules usually have higher latencies associated with them. The table below shows the CAS latency of these modules in ns:

Memory DDR2-800 DDR2-1066 DDR3-1066 DDR3-1333 DDR3-1600
Data Rate 800MHz 1066MHz 1066MHz 1333MHz 1600MHz
CAS Latency 4 5 5 7 9
CAS Latency in ns 5 ns 4.69 ns 4.69 ns 5.25 ns 5.63 ns


From a latency perspective, DDR2 or DDR3-1066 at CL5 is your best bet. However there is a benefit from having more bandwidth; DDR3-1333 delivers 25% more bandwidth but typical DDR3-1333 modules run at CL7 which translates into 12% higher CAS latency than CL5 at 1066.

The chart below shows the performance improvement from running DDR3-1333 (7-7-7-20) vs. DDR2-1066 (5-5-5-15) on the Phenom II X4 955:

In all but two cases the improved bandwidth, but higher latency DDR3-1333 was faster - but the average performance improvement was only 2%. Some applications managed to see a 5 - 6% increase in performance but overall don’t sweat the difference.

Obviously DDR3 is going to do you more good in the long run so it’s what I’d recommend you stick to if you are building a new system. It’s lasted us a long time and we’ve enjoyed its extreme affordability, but DDR2 is finally on its way out.

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  • strikeback03 - Thursday, April 23, 2009 - link

    Well, the most expensive X58 board is over $400, while the cheapest AM2+ boards are under $50, do you want them to say the range is over $350? I'd guess the thinking behind that statement was that you would pair the most expensive processor AMD sells with a higher-end board - the AMD boards top out at about $190, about where the i7 boards start (ignoring rebates). Reply
  • just4U - Friday, April 24, 2009 - link

    It's the minimum entry level into each that I think most people would be curious about. The higher end stuff can really skyrocket the price after all and I am pretty sure it would be filled with features not likely to interest the majority.

  • strikeback03 - Friday, April 24, 2009 - link

    Again though, those who are looking to buy the 955 are probably interested in some of the stuff the better boards offer. Considering the performance available form the 720 or 940 at cheaper prices, I am still doubtful how many people would go for the 955 and the cheapest motherboard possible. Reply
  • duploxxx - Thursday, April 23, 2009 - link

    arrgghh stupied newegg search engine and no edit on anandtech posts

    the msi costs 131, that is still 40$">
  • ssj4Gogeta - Thursday, April 23, 2009 - link

    AMD is getting close and that's a good thing as all of us know. Not that I use AMD, but low prices on Intel chips is good.

    But I think that AMD is soon going to be left behind again when Intel introduces the affordable i5. From what I know the only difference between i7 is that i5 has only 2 channels of RAM and it has the PCIe controller on the package. Surely it won't be too far behind i7 in terms of performance.

    Also can someone clarify whether i5 will be using QPI?
  • duploxxx - Thursday, April 23, 2009 - link

    well then you are one of the so many that have an issue about best price/performance and waht about know, all non i7 buyers are better of pricewise with a AMD based system unless you really want to stick with dualcore for no future at all... . On what planet were you living from 2003-2006 when AMD was the better choice of buying instead off Intel. Reply
  • Sagath - Thursday, April 23, 2009 - link

    Yes, and No. It uses a QPI derivative called CPI if my memory serves correct.

    I dont remember where I read this, so I cannot referance you to it. Nor do I know the difference between the two. Sorry.
  • knutjb - Thursday, April 23, 2009 - link

    AMD still has a long way to go but they are improving. I am glad to see them improve since it pressures Intel to lower prices that benefit the majority of us who can't afford Intel's high end. The closer the competition the better for the consumer, we can't afford to see AMD die off as some joke about. Reply
  • Griswold - Thursday, April 23, 2009 - link

    "..but as applications and workloads become more threaded the i7 could be a wiser long-term purchase. "

    I bought my Q6600 in 2007 and for good reasons (then). I made good use of the four cores - but I've been hearing the above quoted sentence sind 2007 and before but it still has not become true and probably wont before quite some time.

    Where is this "more threaded" and when will it actually arrive? :P

    The situation is such, that I'm definitely going to wait for i5 for the next upgrade and may grab a dualie with hyperthreading, simply because theres only so much I need 4 physical cores for now so it starts to seem like 2 cores plus the two additional logic cores is the more cost efficient and rational way.

    An i7 is definitely not going to be my thing - I just dont need 8 logical cores enough to make it worthwhile.

    But maybe I can stick to my trusty Q6600 long enough for AMD to serve me the perfect solution, maybe with Bulldozer?
  • ssj4Gogeta - Thursday, April 23, 2009 - link

    Why do you look at the number of cores and decide? Look at the performance numbers and decided.

    Besides Hyper threading can't deliver performance boost in all applications. So if you're going 2 cores with hyperthreading you may not see as much performance as 4 physical cores in many apps. You need to look at performance numbers for the apps you most use, not the number of cores.

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