Intel's Core 2 Extreme & Core 2 Duo: The Empire Strikes Back
by Anand Lal Shimpi on July 14, 2006 12:00 AM EST- Posted in
- CPUs
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.
Facebook
Twitter
RSS
202 Comments
View All Comments
invise - Friday, July 14, 2006 - link
According to page 3 "The Test", you used an Intel D975xBX motherboard (Intel 975X chipset) for the tests in the article. Yet in the picture of the Tuniq Tower on page 18 "Overclocking", there is clearly an Asus board with a gold/copper chipset heatsink, blue PCI-Express 16x slot, and alternating yellow and black DIMM slots. Which board is this? I suspect a P5WD2 or P5N32-SLI, just from looking at pictures online, but from what I can find neither of those has a gold/copper heatsink on the Northbridge.I'm curious because you got the board's FSB stable at 445 MHz, which is critical when working with a CPU with a low, locked multiplier. If any other users recognize the board please ID it.
spug1 - Friday, July 14, 2006 - link
I noticed that too Invise. Can we have some clarification as to whether you used the intel board, or the asus p5w-dh for the testing of conroe?!
cheerz, :)
JarredWalton - Friday, July 14, 2006 - link
Overclocking was done with the ASUS board. The benchmarks scores were tested on the Intel board as reported on page 3.Suraj - Friday, October 20, 2006 - link
What other parts did u change when overclocking? I'm very eager to know what exact parts u used when overclocking the e6600.Kiste - Friday, July 14, 2006 - link
Great review, as always. I have to admit though that I was hoping for a bit more with regard to i965 based mainboards.Gary Key - Friday, July 14, 2006 - link
We have a few P965 boards in house currently, however all of them are undergoing almost daily bios changes. They should be very solid from a performance viewpoint within 30 days but at this time they are still immature and any performance results shown with them are not final.
Wesley Fink - Friday, July 14, 2006 - link
You will see Conroe motherboard reviews the first of the week, and yes, there are 965 boards in the reviews.DrMrLordX - Friday, July 14, 2006 - link
Could you guys please do a mini-review of this chip? In particular, could you overclock it using a Tuniq Tower 120 or something and give us some idea of how high it will go? I've been wanting to know more about that proc since AM2 launched, but AMD has been doing a lousy job of getting them into retail channels.redpriest_ - Friday, July 14, 2006 - link
Very detailed, I loved it. But quick question: Your screenshots with cpuid have the stepping as a B1 stepping 5 Conroe - I bought a retail Conroe X6800, and it was a stepping 6 revB2 - and it "only" clocks to 3.466 ghz stably. 3.733 is unstable and 4 ghz is a no boot into Windows; so my question is - is that the stepping you used or was it just a screenshot from an older comparison?Wesley Fink - Friday, July 14, 2006 - link
Our review samples are all Stepping 5. We also have an earlier Stepping 4 unlocked E6700 that overclocks very well. We understood stepping 5 was the Retail stepping. We will clarify this with Intel later today.