FSB Bottlenecks: Is 1333MHz Necessary?

Although all desktop Core 2 processors currently feature a 1066MHz FSB, Intel's first Woodcrest processors (the server version of Conroe) offer 1333MHz FSB support. Intel doesn't currently have a desktop chipset with support for the 1333MHz FSB, but the question we wanted answered was whether or not the faster FSB made a difference.

We took our unlocked Core 2 Extreme X6800 and ran it at 2.66GHz using two different settings: 266MHz x 10 and 333MHz x 8; the former corresponds to a 1066MHz FSB and is the same setting that the E6700 runs at, while the latter uses a 1333MHz FSB. The 1333MHz setting used a slightly faster memory bus (DDR2-811 vs. DDR2-800) but given that the processor is not memory bandwidth limited even at DDR2-667 the difference between memory speeds is negligible.

With Intel pulling in the embargo date of all Core 2 benchmarks we had to cut our investigation a bit short, so we're not able to bring you the full suite of benchmarks here to investigate the impact of FSB frequency. That being said, we chose those that would be most representative of the rest.

Why does this 1333MHz vs. 1066MHz debate even matter? For starters, Core 2 Extreme owners will have the option of choosing since they can always just drop their multiplier and run at a higher FSB without overclocking their CPUs (if they so desire). There's also rumor that Apple's first Core 2 based desktops may end up using Woodcrest and not Conroe, which would mean that the 1333MHz FSB would see the light of day on some desktops sooner rather than later.

The final reason this comparison matters is because in reality, Intel's Core architecture is more data hungry than any previous Intel desktop architecture and thus should, in theory, be dependent on a nice and fast FSB. At the same time, thanks to a well engineered shared L2 cache, FSB traffic has been reduced on Core 2 processors. So which wins the battle: the data hungry 4-issue core or the efficient shared L2 cache? Let's find out.

On average at 2.66GHz, the 1333MHz FSB increases performance by 2.4%, but some applications can see an even larger increase in performance. Under DivX, the performance boost was almost as high as going from a 2MB L2 to a 4MB L2. Also remember that as clock speed goes up, the dependence on a faster FSB will also go up.

Thanks to the shared L2 cache, core to core traffic is no longer benefitted by a faster FSB so the improvements we're seeing here are simply due to how data hungry the new architecture is. With its wider front end and more aggressive pre-fetchers, it's no surprise that the Core 2 processors benefit from the 1333MHz FSB. The benefit will increase even more as the first quad core desktop CPUs are introduced. The only question that remains is how long before we see CPUs and motherboards with official 1333MHz FSB support?

If Apple does indeed use a 1333MHz Woodcrest for its new line of Intel based Macs, running Windows it may be the first time that an Apple system will be faster out of the box than an equivalently configured, non-overclocked PC. There's an interesting marketing angle.

Memory Latency: No Integrated Memory Controller Necessary Power Consumption: Who is the king?
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  • bob661 - Friday, July 14, 2006 - link

    quote:

    So they say 5 years ago until now Intel was “all” crap. I think Northwood was/is very good.
    Sorry but the Netburst stuff is STILL garbage. Core 2 is head and shoulders better than anything they've made since the P3. Although, I thought the power consumption would be better.
    Reply
  • aznskickass - Friday, July 14, 2006 - link

    Man, some AMD fanboys just can't take defeat with dignity.

    Really expensive? Top of the line, sure, but funny you fail to mention the E6300 and E6600, which both offer far better value than the equivalent priced A64.

    Finally match (or even exceed by a few points)?
    OK, here is where I suggest you get your eyes checked out, or go back to school and learn to read graphs. C2D *spanked* A64, not 'match it or exceed it by a little'.

    I think you are just upset that AMDs days as performance crown are over. Tough life being a fanboy eh. You gotta take the ups with the downs son. ;)
    Reply
  • epsilonparadox - Friday, July 14, 2006 - link

    how is a $999 C2E hundreds of dollars more than a $999 FX-62? How is a 55% increase in performance "match (or even exceed by a few points)"? Perhap a slow reading of the article is need. Reply
  • Genx87 - Friday, July 14, 2006 - link

    Intel has a hot chip on their hands here. Problem is, when will it have SLI available?
    And when will we finally see a review using an Nvidia chipset on the AMD side of this equation?
    Reply
  • Bozo Galora - Friday, July 14, 2006 - link

    newegg has started the conroe game by getting a $460 premium on extreme CD2

    http://www.newegg.com/Product/Product.asp?Item=N82...">http://www.newegg.com/Product/Product.asp?Item=N82...
    Reply
  • Bozo Galora - Friday, July 14, 2006 - link

    errr......
    thats a rape of $360, not $460 - my bad (duh)
    Reply
  • bob661 - Friday, July 14, 2006 - link

    It's not on the website anymore. I can't find any Conroe's up their at all. Non-existant. Also, and I know some of you read this but didn't AT say that the supply Conroe would be tight and would drive prices up until the end of the year? So why the bitching about higher prices? If Dell and others are buying up and making supply tight then prices go up. That's the way stuff is.

    Also, who has a Conroe other than the EE that we can buy today? Also, if these CPU's aren't available and today is the launch day then wouldn't this be considered a paper launch? And one more thing, where are the motherboards for this thing?
    Reply
  • yacoub - Friday, July 14, 2006 - link

    technically a paper launch means there were none available at all on launch date. my understsanding is that there were some of these available, they have just been bought up. a limited supply is still better than a true paper launch, imho, even if the end result is the same for most of us - no product available to buy. Reply
  • JarredWalton - Friday, July 14, 2006 - link

    This is a paper launch, and there's a variety of political reasons for it. Among the reasons:

    1 -- AMD is cutting their processor prices in a couple weeks, right after Core 2 Duo was supposed to launch. Intel wanted to launch first.

    2 -- People have been previewing Conroe performance for a while, because they got processors without going through Intel. Some were upset that they couldn't do articles because they didn't want to put in the time or effort trying to get a chip through other sources. By moving up the NDA lift date, Intel now allows all of the web sites to talk about Core 2 Duo in the open.

    Anyway, it's all a marketing war right now, and both AMD and Intel are guilty. Where are the Energy Efficient AMD processors? In about the same place as current Core 2 Duo chips. Basically, though, Intel is building up supply before the official availability launch as opposed to the NDA launch. We might actually be pleasant surprised by availability at the end of the month.
    Reply
  • Shintai - Saturday, July 15, 2006 - link

    How can it be a paperlaunch if they haven´t launched yet? Launch is still july 27th.

    Having sites test an upcoming product is a whole other matter.

    And just because some can buy B2 stepping retail Core 2 Duos from sites already shipping them means nothing.

    Here is a pic of a retail X6800 btw ;)
    http://80.167.217.210/pics/e6800.jpg">http://80.167.217.210/pics/e6800.jpg
    Reply

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