Do Four Cores Need a 1333MHz FSB?

AMD likes to call Intel's quad-core "fake" due to the fact that the chips themselves are composed of two independent dual-core die on a single package. Intel has used this multi-die package approach ever since the dual-core days in order to get CPUs to market quicker and do so at a lower cost. While Intel will eventually move to a single die quad-core design, its current designs are made up of two individual dual-core die.

The problem with Intel's approach is that all traffic from one pair of cores to the next has to go over the FSB, whereas AMD's quad-core Barcelona design places all four cores behind a shared L3 cache. With a single socket quad-core chip, FSB bandwidth is already at a premium given that four cores have to share the same amount of FSB bandwidth that two cores do in a dual-core system. In theory, Intel's quad-core CPUs could stand to benefit more from a 1333MHz FSB than their dual-core counterparts. You may remember from our review of the Core 2 Duo E6750 that the 1333MHz FSB only accounted for an average performance improvement of 1.9% over the 1066MHz FSB, but would things change with four cores running on the other end of that FSB?

To find out we compared the Core 2 Extreme QX6850 to the Core 2 Extreme QX6800, the former running at 3.0GHz on a 1333MHz FSB and the latter 2.93GHz/1066MHz. There is a 2.3% increase in clock speed that the QX6850 enjoys over the QX6800, but we can easily take that into account when looking at the margin of victory in our tests.

The chart below shows the performance increase the QX6850 sees over the QX6800 across our entire suite of benchmarks:

The faster FSB appears to do a little more with the quad-core QX6850 than we saw on the dual core E6750. The performance advantage is not tremendous, amounting to little more than low single-digit percentage point advantages across the board. Taking into account the ~2.2% increase in clock speed that accompanies the QX6850, an average of around a 2% increase in performance is what we'd attribute to the faster FSB.

By no means is it earth shattering or necessary for that point, at least not at these clock speeds. However, given the direction Intel is going in, if you're building a new system today you'll obviously want to opt for a 1333MHz FSB processor. Current quad-core owners shouldn't feel pressure to upgrade, the faster FSB does very little for performance.

A Plan of Attack Affordable Quad Core: AMD Athlon 64 FX-74 vs. Intel Core 2 Quad Q6700
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  • Pirks - Wednesday, July 18, 2007 - link

    again, you're probably right if the silent PC is build with dual core CPU. in my case I've got single core CPU since I don't need any dual core functionality (I mostly play games like Doom 3 and S.T.A.L.K.E.R.), and while dual cores from intel are very solid choice for silent PC - single cores from Intel pretty much suck. hence my choice of AMD San Diego single core chip - that chip turned out to be the best "price/performance/watt for gaming" ratio I could find on ebay :) again, this is all about single core CPUs. I have no idea how the picture looks for dualcores, probably Intel got stronger offer here - by the time I'm about to upgrade to dual core Phenom would be around and we'll see again who wins - AMD very often wins by better price, even when their CPUs are slightly inferior to Intel ones
  • utube545 - Thursday, July 19, 2007 - link

    Oh, STFU already, you dumb fanboy
  • Pirks - Thursday, July 19, 2007 - link

    what, you forgot to put some lube on your blue intel dildo again?
  • Zak - Monday, July 16, 2007 - link

    Looks like the Core 2 Duo E6850 (3.00GHz) is a decent pick for gaming machine until games take full advantage of quad-core CPU.

    Z.
  • jay401 - Monday, July 16, 2007 - link

    Or if you're a budget-conscious gamer, pick up an E4400 for less than half the price and run it at 3.0GHz/1333fsb (drop the multiplier to 9x) which seems to be a pretty common and easy oc with any motherboard capable of 1333fsb.
    Should show little or no performance difference considering the only hardware difference is it has half the cache which doesn't seem to impact games much if at all.
  • sprockkets - Monday, July 16, 2007 - link

    Yep, you want a nice fast platform, get Intel. But I've tested power usage of my Abit nview + 3800+ dual core 65nm processor from AMD, and it takes around 115 watts of energy at full load.

    I think nowadays either you get an ATX gaming system or now try to build the smallest and quietest and coolest mini itx system since they are powerful enough now for most.
  • bobbyto34 - Monday, July 16, 2007 - link

    Yeah for normal home usage, it is interessant to find the best power consumption/ price / performance Ratio.
    AMD X23800+ @ 65€ was an excellent bargain (good performances ingame, though not as good as C2D).

    In some cases, you want only raw performance: usually for work, less time spent waiting, gives you more productivity. At work we have to treat 1gigabyte text files, so the E6700 rocks vs other stations we have (A64 3000+ or P4 3.2Ghz) !
  • kataras - Monday, July 16, 2007 - link

    Hello, just wanted to know is this the Core 2 Duo CPU which has no IHS (internal heatsink) on. Was it hard to remove it, do you need special tools? Did it decrease the temp significantly? I am asking this because i am thinking of either removing IHS or lapping my E6320 as it runs really hot indeed. i would be very pleased if you could answer my questions regarding IHS.
    Thanks
    Ron
  • AMDfreak - Monday, July 16, 2007 - link

    You can find lots of info about removing the IHS over a the xtremesystems.org forums.
  • microAmp - Monday, July 16, 2007 - link

    "... whole 7MHz faster than its predecessor may..." on page 2. Should be 70Mhz faster.

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