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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  • Josh7289 - Friday, July 14, 2006 - link

    When I go to college next year, I know what I'll be buying. :) Reply
  • Pirks - Friday, July 14, 2006 - link

    quote:

    When I go to college next year, I know what I'll be buying. :)
    When I see AMD price cuts next month, I know what your face'll look like. :)
    Reply
  • theoryzero - Friday, July 14, 2006 - link

    This review (and the many others from other review sites) is interesting in that it confirms Intel's bold claims made back in March.

    However, with that out of the way, what I really want to know is which chipset/MoBo to go with? Is springing for high-end memory worth it on Core2? Any plans for a motherboard review in the very near future? Given the Abit AB9 preview and recent articles on DDR2-1000 memory I kind of expected this stuff to show up after the NDA was lifted too.
    Reply
  • Wesley Fink - Friday, July 14, 2006 - link

    Conroe starts shipping July 27th - the original launch date. Intel moved the launch date back two weeks because OEMs like Dell and HP were hot to start advertising and shipping Conroe systems. I suspect Intel was also trying to salvage their NDA. Good news is hard to contain and two more weeks of NDA would have likely resulted in more info leaks that Intel did not want to turn into a flood.

    You will be able to find answers at AnandTech to your basic Conroe motherboard and memory questions early next week.
    Reply
  • theoryzero - Friday, July 14, 2006 - link

    Sounds good, thanks! Reply
  • bob661 - Friday, July 14, 2006 - link

    quote:

    You will be able to find answers at AnandTech to your basic Conroe motherboard and memory questions early next week.
    Thanks.
    Reply
  • Howard - Friday, July 14, 2006 - link

    I would have loved to see minimum FPS as well as average FPS. The review was great otherwise. Reply
  • JarredWalton - Friday, July 14, 2006 - link

    While we could report those scores, we didn't feel we should at least on Oblivion. The reason for that is because the Oblivion runs were manually tested with FRAPS, and the results aren't perfectly comparable between runs. Anyway, here are some of the numbers, but recognize that the margin of error is going to be larger than what you would see with automated timedemos:

    Oblivion Bruma:
    Core E6300: 32-53.7-77
    Core X6800: 47-78.6-117
    AMD 3800+: 27-47.0-72
    AMD FX-62: 38-62.5-94

    Oblivion Dungeon:
    Core E6300: 39-81.3-211
    Core X6800: 57-106.5-214
    AMD 3800+: 35-72.0-189
    AMD FX-62: 46-89.9-211

    F.E.A.R.:
    Core E6300: 34-92-224
    Core X6800: 41-118-310
    AMD 3800+: 28-83-212
    AMD FX-62: 38-101-247

    Rise of Legends:
    Core E6300: 8-68.2-137
    Core X6800: 45-120.5-216
    AMD 3800+: 5-52.1-115
    AMD FX-62: 25-78.4-144

    Minimum frame rates in the Rise of Legends benchmark are zero on most of the Pentium D systems, so again we take those with something of a grain of salt. Regardless of how you look at it, though, the Core 2 Duo processors consistently outperform their AMD equivalents in gaming results. We will be looking at additional games next week in our motherboard reviews.
    Reply
  • nowuadmit - Friday, July 14, 2006 - link

    First off, when u guys reviewed a 486/33 for the first time... it was also "the fastest piece of silicon the world has ever seen"... then later, when u saw the P2-550... THAT was the "fastest piece of silicon... blah blah".

    Well its nice that intel has made a really expensive and barely available new chip, so they can finally match (or even exceed by a few points) AMD's reasonably priced previous generation. So now u can say they have the fastest, and if u want to spend thousands on a CPU that is only slightly faster than something that costs hundreds of dollars, HEY BE MY GUEST! there have been worse wastes of money! (in theory anyways, since the avg american wont be able to actually find any of these in the local stores for quite some time, if intel follows their previous habits).

    Anyhow the point of my comment... i think this is a good thing. i mean, anything that actually causes an intel fanboi to admit finally that intel has been reaming your butts for 5 years..

    while the people who simply buy whatever CPU makes the most sense have been enjoying getting great quality nookie from AMD! SO i present to you, this Technical Quote of the Year, spoken on behalf of all intel fanbois with half a brain!

    Technical Quote of the Year:

    "...power hungry, poor performing, non-competitive garbage (sorry guys, it's the truth) that Intel has been shoving down our throats for the greater part of the past 5 years."

    Congradulations on your honesty, finally.
    Reply
  • MrKaz - Friday, July 14, 2006 - link

    Yes that’s truth.

    80% of Intel crap, only 20% is good. The Pentium M.

    So they say 5 years ago until now Intel was “all” crap. I think Northwood was/is very good.

    My maximum price is 100$ (or 120$ with cooler) for a CPU. Only AMD as an honest performing CPU for those prices.
    Reply

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