The introduction of Core 2 Duo about a month ago delivered a new processor with about a 25% improvement in performance over the fastest chips in the market. The top-line X6800, running at 2.93GHz, was the most flexible of the new processors, with completely unlocked multipliers up and down. This allowed settings like running at a 13x multiplier (stock is 11x) at 277 FSB (3.6GHz) at default voltage - the result of the incredible head room exhibited by the new Conroe processors.

Intel Core 2 Processors
CPU Clock Speed L2 Cache Price
Intel Core 2 Extreme X6800 2.93GHz 4MB $999
Intel Core 2 Duo E6700 2.66GHz 4MB $530
Intel Core 2 Duo E6600 2.40GHz 4MB $316
Intel Core 2 Duo E6400 2.13GHz 2MB $224
Intel Core 2 Duo E6300 1.86GHz 2MB $183

Unfortunately, the X6800 costs $999 which is way out of the budget range for many buyers - and it's even more at retail right now due to demand and availability, with the best price we're currently tracking at $1150. The good news is the lowest-priced E6300 outperformed every previous Intel chip. Compared to AMD the E6600 outperformed every AMD processor, and costs $364 to $433 compared to the $825 to $950 for the AMD top-line FX-62. (Almost all of the Core 2 processors are being marked up 10% to 20% at retail, though we expect prices to drop over the coming months.)

So is there a catch? The answer is yes and no. The X6800, as stated, is unlocked up and down, allowing the flexibility to do anything you wish with the outstanding head room of the Core 2 Duo architecture. The rest of the Core 2 Duo chips are hard-locked up and down, which greatly limits the flexibility of the head room which often runs 1000MHz, 1500 MHz, or more - depending on the CPU and motherboard. You could only access this extra power at the stock multiplier. This is actually a big negative compared to AM2 processors, where all chips are at least unlocked down.

ASUS has a history of incredible creativity in their mainstream motherboards. Those who recall the P865 Springdale will remember ASUS was the first to implement the "875 only" PAT speedup on the mainstream 865 - making the 865 just as fast as the more expensive 875. On the 925, where Intel had implemented a clock lock, ASUS was the first to find a way to break the clock lock and unleash extended speeds on their 875 motherboards. With this history in mind, it should not come as a surprise that ASUS has just introduced some very creative thinking in a new BIOS for their 965P chipset P5B Deluxe motherboard.

The new 0507 BIOS for the P5B Deluxe, dated 8/10/2006, has two new and exciting features:
  1. Provide better maximum overclocking.
  2. Add the ability to adjust the multiplier of most Conroe CPUs even if they are not Extreme Edition.
The P5B reached about 362x10 in testing for the Conroe Buying Guide: Feeding the Monster. This provides a baseline for comparing the new BIOS to previous results.

Even more exciting is that ASUS says they have found a way to unlock up or down most Conroe chips. This will be a significant new feature that is highly desired by many Core 2 Duo buyers. It didn't take but a few minutes for us to get the new BIOS flashed and a Core 2 Duo chip mounted to check this out.

A pattern has been developing for some time in test results from Core 2 Duo chips. The 2MB Cache chips, the E6300 and E6400, are generally overclocking a bit better than the 4MB E6600, E6700, and X6800 chips. Since performance of the 2MB is a bit lower than the 4MB cache at the same frequency, this means you can make up for some of the 2MB cache deficiency with the ability to run at a faster speed. With this in mind, testing was performed with all 4 of the Core 2 Duo chips that are multiplier locked - the 4MB E6700 and E6600, and the 2MB E6400 and E6300.

E6700 & E6600 – 4MB Cache


View All Comments

  • BuddyHolly - Friday, August 25, 2006 - link

    Thanks Wesley for the info on running the memory in spec. That is exactly what I was looking for.
    When I am asking for benchmarks, I would love to see PI and a few others run at the same clock speed but different FSB to show what gain we get from this..for example
    The 6300 at the following:
    What type of gain to we get from jacking up the front side bus? I know it used to help a lot on my old Barton's, but what does it get us with the Core 2?
    Great article and interesting discussion. One of the things I truly love it the fact that the staff at AT respond to these post and realy add a lot to the discussion.
    Thanks again!
  • BuddyHolly - Friday, August 25, 2006 - link

    I have a few questions that were not covered
    1) Can we have some benchmarks showing the benefit of running up the FSB vs standard at the same clock speed. I know on some processors in the past this gave a nice boost in performance, but how much are we talking here? Huge gains or just a few percent?
    2) Can we lock the memory on these boards and crank the FSB up with cheap memory? If so, what are the benifits the same?
    Thanks for the article. I too got excited at seeing the title, hoping for a return to the golden days of overclocking without multiplier locks....
  • Wesley Fink - Friday, August 25, 2006 - link

    DDR2-533 is the 1:1 strap and theoretically provides the highest memory bandwidth. DDR2-533 memory setting hits DDR2-800 at 400FSB. Almost all of the cheap memory based on Elpida chips can do DDR2-800 4-3-3 as you saw in the Conroe Buying Guide. At the highest multiplier of x7, then the E6300 maxes out at 2.8GHz, with plenty of headroom left.

    Dropping the memory to DDR2-400 you would reach DDR2-800 at a FSB of 533, which covers all the headroom we found with the E6300. You have even more flexibility with the E6400 with the higher x8 multiplier.

    The point is you should be able to reach pretty high in headroom even with cheaper memory. Of course the high-end DDR2 all reached DDR2-1067 to DDR2-1100, which gives even more flexibility for maxing headroom at the fastest memory timings possible.

    As for benchmarks, we provided Super Pi times in several of the higher overclocks as a quick bench, You can easily compare these results to what you achieve. Super Pi is a free program that's easy to run. Version 1.5 is a modified version for benchmarking available at

  • shabby - Saturday, August 26, 2006 - link

    So the p5b has a ddr2-400 setting? I thought the lowest was a 1:1 ratio(533 setting). Reply
  • Gary Key - Saturday, August 26, 2006 - link


    So the p5b has a ddr2-400 setting? I thought the lowest was a 1:1 ratio(533 setting).

    If you are using a P4 then the DDR2-400 setting is the base setting on this board.
  • shabby - Sunday, August 27, 2006 - link

    And if its a c2d then your outta luck? Reply
  • kmmatney - Friday, August 25, 2006 - link

    We are talking about some pretty huge gains here. Just look at the new speeds, and waht the equivalent cpu would cost running at those speeds. You gain the same performance of cpu's which can cost hundreds of dollars more.

    I agree wiuth your second question. I would like to see how things work out using a memory divider (do Conroe motherboards even use memory dividers?).
  • KHysiek - Friday, August 25, 2006 - link

    In "Conroe Buying Guide: Feeding the Monster" Deluxe model was featured, here we have (I suppose) P5B regular. P5B non-dlx have less overclocking options (lika limited memory voltages), this have serious impact on o/c possibilities.
    In new BIOS we stilla have just 2.1 DDR2 max voltage?
  • junior1 - Friday, August 25, 2006 - link

    New records for FSB is interesting, but I think the question that many of us have is: Is there an opportunity for getting more bang for the buck?

    Assuming that upwards unlocked chips are rare, the budget-constrained conroe buyer can

    a.) Crank a cheaper CPU to high FSB, with expensive RAM and motherboard. Drop the multiplier if needed to take the system to its top performance, or

    b.) Save money by buying value RAM and a mid-range motherboard, and spend that extra budget on a CPU with a higher max multiplier. The max FSB will not be so exciting, and the memory may have to run at a slower ratio, but the CPU core should be quite high.

    Which of these two schools of thought will perform the best for the price? Of course it will vary on a case-by-case basis, but an investigation would be very relevant.

    My guess is that the $300 or so required to get a high FSB mobo and fancy RAM would be better spent on a higher multiplier. Does anyone have any thoughts on this?

    (Finally, I would also like to throw in my request for a review of the Gigabyte P965-DS3, as it seems to be the cheapest available Core2 motherboard with real OC potential.)
  • Janooo - Friday, August 25, 2006 - link

    That's very good question. An answer would depend on what is your box meant for.
    It appears though that most of the applications are more "memory hungry" than CPU limited. That's why FSB speed is very important to overclockers.

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