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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  • yuhong - Monday, January 4, 2010 - link

    "The Clarkdale lineup is honestly made up of CPUs that are too expensive. The Core i5 670, 661/660 and 650 are all priced above $170 and aren’t worth the money. The problem is Lynnfield’s turbo mode gives you high enough clock speeds with two threads that there’s no need to consider a dual-core processor. You can buy a Core i5 750, have more cores than any of these Clarkdales and run at close enough to the same frequencies for $196."
    But then you have to pay extra for a discrete graphic card and not every application need the extra graphic power!
    Reply
  • Paulman - Monday, January 4, 2010 - link

    Wow, I was going to write about how you wouldn't have to buy a discrete graphics card if you went with a Core i5 750 because you could just choose a motherboard with an integrated graphics chip. But then I checked online and it seems that there aren't any P55-based boards with integrated graphics - wow! Wouldn't have believed it myself.

    However, Anand's point still stands when comparing the Clarkdale i5's to the Phenom II X4, for which you can get many boards with integrated graphics.
    Reply
  • Inkie - Sunday, January 10, 2010 - link

    "when comparing the Clarkdale i5's to the Phenom II X4, for which you can get many boards with integrated graphics"

    ...but Clarkdale already has integrated graphics.
    Reply
  • ssj4Gogeta - Friday, January 8, 2010 - link

    It's because P55 is a southbridge, not a northbridge. Reply
  • Taft12 - Monday, January 4, 2010 - link

    But then you have to pay extra for a discrete graphic card and not every application need the extra graphic power!

    Only if you don't already have any PCI-E x16 card. Is that true for a single reader of this site? And truly ANY PCI-E card will perform better than Intel's on-chip solution, even one 3 generations old.
    Reply
  • ereavis - Monday, January 4, 2010 - link

    so the price goes up another $30-$40. As to your question of truth, yes I spend 40 hours a week on an intel IGP dual core as it is, so do the other 1000 people in this building doing engineering work that's processor demanding but graphics independent. Reply
  • nubie - Monday, January 4, 2010 - link

    There are rafts of HP 8400 OEM pci-e cards on ebay right now for $15 (total, no shipping or tax), that should even accelerate your Flash 10.1 and video just fine.

    If you even need it that is, and it is clear that for many there is absolutely no use for more than the integrated graphics.
    Reply
  • oc3an - Monday, January 4, 2010 - link

    Hi Anand. Looks to me like something weird is up with your Everest benchmarks. Shouldn't the 24X multiplier have the faster scores?

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

    Hi Patrick,

    Fixed it, the images were reversed.

    Thanks!
    Raja

    Reply
  • maxfisher05 - Monday, January 4, 2010 - link

    Good Article Anand. I'm going to be building my first HTPC soon, but I want to be able to do some light gaming on it, and it doesn't look like the integrated graphics have come far enough yet. If the 661 was priced lower I would consider it, but for nearly the price of a 750 you are right in saying it makes no sense. 750 + 5750 discrete graphics for me please :)

    Will someone be posting an updated system buyers' guide soon?
    Reply

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