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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  • Taft12 - Monday, January 4, 2010 - link

    The parent's office PC's aren't bottlenecked by the OS - they're not bottlenecked PERIOD. They run modern productivity apps just fine and would gain little to no benefit from Core i3 (or Windows 7 for that matter).
  • Paulman - Monday, January 4, 2010 - link

    Those office PC's you mentioned aren't bottlenecked by the 2GB of RAM. But I wouldn't say that they aren't bottlenecked, "period". What they ARE bottlenecked by is disk I/O, I'm sure. Throw in a good SSD and you would notice quite a bit of speed improvement, and probably a noticeable difference between the 1.6GHz and 2.4GHz machines.

    The most annoying thing to me whenever I'm using my PC is seeing and hearing my laptop HDD thrash around when launching an app or what not, because everything is held up as a result. Yes, I know it's a laptop HDD, but desktop drives are pretty slow, too.
  • FlyTexas - Monday, January 4, 2010 - link

    SSDs are indeed fast, and make the whole computer feel "snappier"...

    However, these office machines never shut down (they hibernate overnight). IE8, Word, Excel, and Acrobat are always open and always stay open. Once loaded in memory, the hard drive is hardly used.

    I've looked at upgrading them to 3GB of RAM, but they aren't using what they have, so why bother? Most of them use right around 1GB of RAM most of the time.

    Could we put 40GB SSDs in? Sure, they are about $130 at Newegg right now... Not the end of the world, until you multiply that times 24 machines. Not a minor expense.
  • FlyTexas - Monday, January 4, 2010 - link

    That is so true. This the first time in a long time that the computers have been "fast enough" for everything we use them for.

    There was a time in 1993/1994 that we were in this position, running DOS 6 and Windows 3.1 on 486DX2/66 machines, where the move to the DX4/100 or Pentium saw no benefit until Windows 95 came out. I worked in small shop back then, and we demoed a Pentium 66 machine, and saw zero benefit over the 486DX2/66 machines, other than it cost twice as much.

    Perhaps in 2002, the Athlon XP machines were "fast enough" for Windows XP and Office XP, that was a nice time as well in the business. A Pentium III 550mhz was my last personal Intel chip until 2006, when I got my first Core2Duo machine at home. I had to work with some Pentium 4s at work during that time, Intel really, REALLY dropped the ball with the Pentium 4, IMHO.

    Oh well... I've been doing this a long time, I still remember 5.25" floppy drives, with NO hard drive and those ugly green monitors with Hercules graphics... :)
  • lowlight - Monday, January 4, 2010 - link

    But the 45nm package on Westmere doesn't just carry the GPU. They also moved the PCI-E controller and Memory controller there. I guess the "CPU" is still technically 32nm, but compared to Nehalem, half the "CPU" actually resides on a 45nm package on the chip...

    You can see a diagram in this Clarkdale review:">
  • lowlight - Monday, January 4, 2010 - link

    Guess I should have read the whole review... You guys picked it up too! Not many others did though ;)
  • ilnot1 - Monday, January 4, 2010 - link

    I swear I've scoured the pages but I don't see your Test System Setup Chart: how much RAM, which graphics card? If it is there and I missed it I wish you could delete posts.
  • Spoelie - Monday, January 4, 2010 - link

    It's on page 6

    I'd like to know the setup of each memory benchmark on page 2. What memory speeds and settings were used for the latency and bandwidth numbers?
  • Anand Lal Shimpi - Monday, January 4, 2010 - link

    All of the CPUs used DDR3-1333 running at 7-7-7-20 timings for that test. I used Everest 1909 (I believe, I'm about 2300 miles away from my testbed right now :-P) and CPU-Z's latency tool to grab the data.

    Take care,
  • toyota - Monday, January 4, 2010 - link

    I was looking for it too and its not there.

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