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DDR3 Memory Scaling On AMD's Phenom II X4

DDR3 Memory Scaling On AMD's Phenom II X4
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DRAM prices have come down in the past few months, making capacities of 4, 6, or 8 GB very affordable. You can get 4 x 2 GB DDR2 memory kits starting at only $80, and even DDR3 is no longer unattainably pricey. However, high-speed memory is still considerably more expensive, and memory vendors want you to believe that DDR3-1600 and faster is what you need, despite the fact that neither Intel's Core i7 or AMD's Phenom II X4 officially support those data rates. We wanted to look into this, and so we ran plenty of benchmarks on an AMD Phenom II X4 955, with all possible memory speeds and different timings.

Where Memory Differs

Two types of Dynamic Random Access Memory (DRAM) technology currently dominate: DDR2 and DDR3 at speeds between 400 MHz and 1000 MHz. DDR stands for Double Data Rate, which means that data is transferred during the rising as well as the falling edge of a clock cycle, which doubles the effective clock rate. The slowest mentioned memory is therefore referred to as DDR2-800 (400 MHz in DDR mode). DDR2 is typically available at speeds up to DDR2-1066 or DDR2-1200, while DDR3 spans DDR3-800 to DDR3-2133+ speeds.

PC memory is available as DDR2 or DDR3 modules, generally called Dual Inline Memory Modules (DIMMs). Notebook memory comes on small outline DIMMs (SO-DIMMs), which are much smaller, but otherwise very similar. Intel’s Core i7 processors support up to three memory channels, meaning you can use three or six memory modules operating in three-channel mode at maximum speed, while most other architectures work with two or four modules in a dual-channel configuration. This applies to AMD’s Athlon 64 X2 and Phenom series, as well as Intel’s Core 2 and Pentium families. Multi-channel modes are an effective way to increase memory bandwidth by aggregating multiple 64-bit links.

Now, you probably know that a memory kit running at a high speed is probably the best choice for a fast system, but you’ll find that there is a plethora of different brands and products, and the differences between them often seem to be small. As a matter of fact, the remaining differences can be found in the voltage level and the supported operating parameters, known as timings. These basically define the number of clock cycles required for each of the key steps in accessing the memory matrix. As a result, greater timing values represent slower execution.

Which Memory Should You Buy?


We will answer this question on the following pages by looking at a modern AMD Phenom II X4 955 system, which we benchmark at many different memory speeds and timings to find the best bang for your buck. We'll be doing the same thing in a subsequent piece for owners of Intel processors, so keep an eye out for that!

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  • 6 Hide
    cangelini , June 4, 2009 6:50 AM
    judeh101DDR3 memory scaling on AMD's Phenom II X4, why don't cha do one for Intel as well? I'd love to see the performance on the Core i7 platform


    It's coming!
  • 0 Hide
    cangelini , June 4, 2009 7:45 AM
    Much thanks judeh, I appreciate your feedback!

    Best,
    Chris
  • 6 Hide
    Antman56 , June 4, 2009 7:59 AM
    The real trick to seeing a greater discrepancy between different clock speed memory(s) could be done by overclocking the CPU-NB. Using SiSoftware Sandra, I get 13.2 GB/s with DDR2 @ 1066 MHz (5-5-5-15) on a 3.4 GHz Phenom II 940 X4 with a 2.4 GHz CPU-NB.

    Overclocking that Integrated Memory Controller is key!

    ...Just a suggestion :p 
  • -2 Hide
    empstar , June 4, 2009 8:34 AM
    why always missing something..... where's the DDR2 RAM ?? should include in the chart!! very disappointed.
  • 0 Hide
    EQPlayer , June 4, 2009 8:47 AM
    Yarr, good point. Overclocking the CPU/NB on these chips seems to have nearly (well that might be a bit of an exaggeration) as much of an effect as overclocking the CPU itself.
  • -1 Hide
    DjEaZy , June 4, 2009 9:25 AM
    ... it is getting better and better with TOM's... more information to compare... for the last month it's enjoyable to read...
  • 0 Hide
    Anonymous , June 4, 2009 10:16 AM
    Why you didn't have tried a 'synchronized' configuration with base clock, north-bridge, memory and cpu core running on integer or semi-integer divisors ? like 266MHz base clock, 1068 MHz memory clock, 2136 MHz north bridge & HT clock and 3199 core clock.
    This configuration is possible even with DDR2, with lower latencies memories and is much closer to the DDR3/1333 configuration than you think.
  • 2 Hide
    cinergy , June 4, 2009 10:43 AM
    Very nice bench for AMD people.
  • -7 Hide
    apache_lives , June 4, 2009 10:59 AM
    judeh101DDR3 memory scaling on AMD's Phenom II X4, why don't cha do one for Intel as well? I'd love to see the performance on the Core i7 platform


    Why does everyone vote down a valid question?
  • -1 Hide
    apache_lives , June 4, 2009 11:04 AM
    and this is the same old picture - mainstream ram has always been the best price:p erformance, no point in chancing extreme memory, and "high end" memory is only good for overclocking etc
  • -1 Hide
    chripuck , June 4, 2009 11:47 AM
    apache_livesand this is the same old picture - mainstream ram has always been the best priceerformance, no point in chancing extreme memory, and "high end" memory is only good for overclocking etc


    I wouldn't call the two top performers mainstream... with those timings there at least a step above main stream. Now to your point they're definately not the top of the line, but anyone with a clue about electronics knows the best bang for your buck is never the cheapest and never the most expensive... the sweet spot is always in the middle.
  • -3 Hide
    Kill@dor , June 4, 2009 12:39 PM
    Can't wait for Intel's review as well.
  • 1 Hide
    coopchennick , June 4, 2009 12:43 PM
    Soo... I guess Toms just decided not to do the SBM giveaway?
  • -1 Hide
    Kill@dor , June 4, 2009 1:00 PM
    I have to kind of admit this was a little unfair because DDR3 2000 was not in this line up...why i'm not sure. Intel's processors can utilize DDR3 2000 very well with timings like 9-9-9. But even so, its important to show how DDR3 2000 can perform with AMD and the benefits it has for a stable high clock on your system. If you plan on overclocking 3.0GHz to about 3.6 or 3.8 DDR3 1333-1600 is key in my opintion. Anything higher than 4.0GHz will benefit stability with DDR3 2000. I hope Toms can get a review to show this...
  • -1 Hide
    buzznut , June 4, 2009 1:31 PM
    I was disappointed that the memories weren't tested more with overclocking. You did a little bit with the 800 speed, but who is gonna run their ram at that speed?

    Well, nice article. It makes me wonder why ddr3 memory is not more effective, does not offer much beyond ddr2. It seems to make a considerable difference in video cards, ddr2 vs ddr3. Will they skip ddr4 and go to ddr5 for mainboard memory, like the upper end ATI cards?

    As it has been for a few years, latency is the most important factor with AMD processors.
  • 0 Hide
    sublifer , June 4, 2009 1:57 PM
    Only testing in 2T command rate?
  • 2 Hide
    Anonymous , June 4, 2009 2:26 PM
    Quote "Why does everyone vote down a valid question?"

    Because if that person would have read the first page of the article, they would have seen that a Intel article is coming.......
  • 2 Hide
    HVDynamo , June 4, 2009 2:30 PM
    apache_livesWhy does everyone vote down a valid question?


    Because it says there is an intel article to follow at the bottom of the first page of the article. He posted before reading.
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