The Return of Hyper Threading

While Nehalem is designed to scale to up to 8 cores per chip, each one of those cores has the hardware necessary to execute two threads simultaneously - yep, it's the return of Hyper Threading. Thus our quad-core Nehalem sample appeared as 8 logical cores under Windows Vista:

Four cores, eight threads, all in a desktop CPU

Note that as in previous implementations of Hyper Threading (or other SMT processors) this isn't a doubling of execution resources, it's simply allowing two instruction threads to make their way down the pipeline at the same time to make better use of idle execution units. Having 8 physical cores will obviously be faster, but 8 logical (4 physical) is a highly power efficient way of increasing performance.

We took Valve's source-engine map compilation benchmark and measured the compile time to execute one instance (4 threads) vs. two instances of the benchmark. The graph below shows the increase in compilation time when we double the workload:

Valve Map Compilation Benchmark - 4 to 8 Thread Scaling

While the 2.66GHz Core 2 Quad Q9450 (Penryn) takes another 127 seconds to execute twice the workload, the 2.66GHz Nehalem only needs another 49 seconds. And if you're curious, this quad-core Nehalem running at 2.66GHz is within 20% of the performance of an eight-core 3.2GHz Skulltrail system. Equalize clock speed and we'd bet that a quad-core Nehalem would be the same speed as an 8-core Skulltrail here. The raw performance numbers are below:

Valve Map Compilation Benchmark 

We couldn't disable Hyper Threading so we reached the limits of what we were able to investigate here.

The Socket A Quick Path to Memory
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  • weihlmus - Friday, September 5, 2008 - link

    is it just me or does lga1366 bear more than apassing resemblance to amd's logo...

    if only they could have crammed it into 1337 pins - "nehalem - the 1337 chip"
  • Proteusza - Friday, July 11, 2008 - link

    I see that on the Daily Tech main page, the headline for this article now reads:
    "June 5, 2008
    Post date on AnandTech's Nehalem preview, before it was ripped and republished on Tom's Hardware"

    Does anyone know what happened? I cant find the same article on Tomshardware, I presume they took it down.
  • xsilver - Friday, June 20, 2008 - link

    10 pages of comments and not one about the future of overclocking?

    No more FSB = no more overclocking??????
    Enthusiasts might jump ship if overclocking usually brings 20% extra performance, all amd have to do is come within 10% on performance and below on price?
  • Akabeth - Thursday, June 19, 2008 - link


    This pretty much makes it pointless to purchase any high tier mobo and quad core today... It will be eclipsed in 6 months time...

    Some of the numbers here make me wonder, "Are you f*cking kidding me?"
  • JumpingJack - Friday, June 13, 2008 - link

    Anand, you could clear up some confusion if you could specify the version of windows you ran. The screen shots of some of your benchmarks show 64-bit Vista, yet your scores are inline with 32-bit Vista.... it makes a difference.
  • JumpingJack - Friday, June 13, 2008 - link

    Nevermind, page 2 shows 32-bit Vista... makes sense now. You should becareful when posting stock photos, the Cinbench reflects 64-bit.
  • barnierubble - Sunday, June 8, 2008 - link

    It appears to me that the Tick Tock cycle diagram is wrong.

    Conroe shooked the world in the second half of 2006, Penryn came in the second half of 2007, now 2008 we have Nehalem on the horizon set for the second half of this year.

    Now that is 2 years between new architectures with the intermediate year bringing a shrink derivative.

    That is not what the diagram shows; bracketing shrink derivative and new architecture in a 2 year cycle is clearly not fitting the reality.

  • mbf - Saturday, June 7, 2008 - link

    Will the new IMC support ECC RAM? And if so, what are the odds the consumer versions will too? I've had a bit of bad luck with memory errors in the past. Since then I swear by ECC memory, even though it costs me a bit of performance. :)
  • Natima - Saturday, June 7, 2008 - link

    I just thought I'd point out that the Bloomfield chip reviewed (to be released in H2 2008) will infact dominate the gamer/high-end market.">

    The smaller sockets will be for what I like to call... "office PC's".
    And the larger socket for high-end servers.

    A majority of custom PC builders will be able to buy & use Nehalems by the end of the year. Hoorah!
  • Natima - Saturday, June 7, 2008 - link

    The article semi-implied that chips for the PC enthusiast would not be out until mid-2009. Just wanted to clarify this for people.

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