Memory Performance - Not Very Nehalem

Let’s start at the obvious place, memory performance. Nehalem moved the memory controller on-die, but Clarkdale pushes it off again and over to an on-package 45nm graphics core.

To make matters worse, the on-package chipset is a derivative of the P45 lineage. It’s optimized for FSB architectures, not the QPI that connects the chipset to Clarkdale. Let’s look at the numbers first:

Processor L1 Latency L2 Latency L3 Latency
Intel Core i7-975 4 clocks 10 clocks 34 clocks
Intel Core i5-750 4 clocks 10 clocks 34 clocks
Intel Core i5-661 4 clocks 10 clocks 39 clocks
AMD Phenom II X4 965 3 clocks 15 clocks 57 clocks
Intel Core 2 Duo E8600 3 clocks 15 clocks  


L1 and L2 cache latency is unchanged. Nehalem uses a 4-cycle L1 and a 10-cycle L2, and that’s exactly what we get with Clarkdale. L3 cache is a bit slower than the Core i7 975, which makes sense because the Core i5 661 has a lower un-core clock (2.40GHz vs. 2.66GHz for the high end Core i7s) Intel says that all Clarkdale Core i5s use the same 2.40GHz uncore clock, while the i3s run it at 2.13GHz and the Clarkdale Pentiums run it at 2.0GHz.

Processor Memory Latency Read Bandwidth Write Bandwidth Copy Bandwidth
Intel Core i7-975 45.5 ns 14379 MB/s 15424 MB/s 16291 MB/s
Intel Core i5-750 51.5 ns 15559 MB/s 12432 MB/s 15200 MB/s
Intel Core i5-661 76.4 ns 9796 MB/s 7599 MB/s 9354 MB/s
AMD Phenom II X4 965 52.3 ns 8425 MB/s 6811 MB/s 10145 MB/s
Intel Core 2 Duo E8600 68.6 ns 7975 MB/s 7062 MB/s 7291 MB/s


Here’s where things get disgusting. Memory latency is about 76% higher than on Lynnfield. That’s just abysmal. It’s also reflected in the memory bandwidth scores. While Lynnfield can manage over 15GB/s from its dual-channel memory controller, Clarkdale can’t break 10. Granted this is higher than the Core 2 platforms, but it’s not great.

What we’re looking at is a Nehalem-like CPU architecture coupled with a 45nm P45 chipset on-package. And it doesn’t look very good. If anything was going to hurt Clarkdale’s performance, it’d be memory latency.

Index Clarkdale: The Perfect Home Theater PC
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  • rainman1986 - Monday, January 4, 2010 - link

    I'm puzzled by the results for this cpu, I'd have thought it would be close to the 920, but it was much slower than the i3 and i5.

    Did I miss something?
  • rainman1986 - Monday, January 4, 2010 - link

    Sorry, not the 860, the 870 was slower (but the 860 would have been just a little slower than that!)

    Still, what gives?
  • deruberhanyok - Monday, January 4, 2010 - link

    Possible responses:

    "I had no idea it had a retro mode!"

    "So these processors can run Ultima IX acceptably then?"

    "My eyes! The goggles, they do nothing!"

    "Intel HD graphics: bringing extreme video quality to 2001's hottest titles!"

    And so on.
  • vol7ron - Monday, January 4, 2010 - link

    The Clarkdale Unencrypted score is shown, could you also display the Lynnfield Unencrypted score.

    To use the unencrypted Clarkdale as the control for Lynnfield doesn't seem right since there are differences between the two procs. It would make more sense to compare
    [Lynnfield Encrypted Score]/[Lynnfield Unencrypted Score] to [Clarkdale Encrypted Score]/[Clarkdale Unencrypted Score]

  • SydneyBlue120d - Monday, January 4, 2010 - link

    Thanks a lot for the great review!

    When You'll be back from CES, I'd like to see a test of:

    - Pentium G9650 (the great absent for the corporate/office world);
    - Flash 10.1 and BR/MKV HTCP with integrated gfx;

    Thanks a lot :-)
  • SydneyBlue120d - Monday, January 4, 2010 - link

    Forgot to ask:

    Is the integrated gfx DX 10 or 10.1? Will it support Direct2D?

  • ruetheday - Friday, January 8, 2010 - link

    yes to DX10 and Direct2D
  • vol7ron - Monday, January 4, 2010 - link


    Good article. I like how you re-addressed topics that you originally discussed on the opening page, with a more concise statement on the pages that followed. For instance, when talking about the memory on/off die. You gave a decent bit of info on page 1 and then a quick rememberance on page 2.

    --- More will come once I finish reading the artice :) ---

  • Rajinder Gill - Monday, January 4, 2010 - link

    Credit goes to Anand for this piece. I only chimed in on the OC side. :)

  • vol7ron - Monday, January 4, 2010 - link

    I noticed something fishy when it said thanks to Raja for the Mobo suggestion. I guess the article's author threw me off :)

    Great collaboration, regardless.

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