As you will see in our upcoming roundups, Asus has been very successful in working around the problems with the Intel Overclock lock on the 925X/915 chipsets. Abit employs similar techniques in their workaround with similar success, but Abit still tops out at about 260 with our SATA hard drive.

This screen capture of an Asus P5AD2 was made on the same core test bed used in our DDR2 memory roundup. We are using Asus BIOS version 1.05 Beta 2, but we have found that any BIOS version 1.04 or above will provide the same potential performance. CPU voltage is default 1.3875V, DDR2 memory voltage is 2.0V, and termination voltage is set to 1.2V. The video card for this screen capture is the ATI X800 XT, since any of the nVidia PCIe cards that we tested topped out at 250 -260 CPU clock.

We were finally able to determine the limit of our DDR2 memory in the unlocked Asus P5AD2. We were able to reach DDR2 733 with the just released Corsair DDR2 667 and the just-released Crucial Ballistix DDR2 667 memory. We also found that DDR2 667 branded memory, based on specially selected DDR2 533 memory chips, does indeed perform better above DDR2 683 than the DDR2 533 labeled DIMMs. DDR2 voltage was 2.0V. The DDR2 memory that we tested could not run at stock Intel settings (3:4) above DDR2 733, and the top screen capture at 278 uses a lower ratio for memory.

It should be clear by now that the simple explanations for the Overclock lock, which are circulating on the web as facts, are, at best, half-truths. To effectively reach the performance limits of DDR2 memory and current Socket 775 Prescotts on the 925X/915 requires manipulation of the PCI Express frequency at boot and the link frequency for the chipset. While increases in voltage to the chipset will allow for higher overclocks, this method does not solve the main problem of controlling PCIe/link frequencies to levels that are usable in the overclocked machine.

Breaking the Overclock Lock


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  • danidentity - Saturday, July 17, 2004 - link

    It's only a matter of time until AMD starts limiting overclocking just as Intel is doing now. Don't forget how Intel used to be the only one with locked multipliers. AMD then followed suit.

    Anand, do you plan on doing an article to see how well the off-the-shelf LGA775 chips themselves scale with OCing?
  • neologan - Saturday, July 17, 2004 - link

    #4, i do not agree. Because of DDRII and the hugely overclockable Prescotts, the potential for massive Intel overclocks without extreme cooling and wads of cash would be huge. They are trying to limit this as much as possible - that is what the lock is for. They are not doing this out of spite just because enthusiasts are not picking there platform, they are doing it because if there was no lock, we would be seeing massive overclocks at low prices of the likes we have never seen before. Intel can go to hell imo....AMD all the way. They have, for a long time either provided amazing value and competitive performance, or equal prices with better performance. Reply
  • Anemone - Saturday, July 17, 2004 - link

    Because when the 875 was around Intel had a competitive set of cpu's. Now, Intel figures that those in the know aren't buyng their cpu's. There are easily a dozen websites that are recommending AMD64 when it comes to current machine builds. So Intel figures the only ones buying their machines are the Dell purchasers of the world. If that is true then why build a chipset that helps enthusiasts?

    I get the strong feeling that Intel doesn't feel they CAN compete anymore in the enthusiast arena, that each time they release a more competitive CPU, AMD will just one up them. So, they are figuring why bother. Remember Intel is lead around by the marketing department. They lock things down, and get two results. They guarantee a simple, solid non overclocking chipset, thus making sure that the people buying their stuff are the run of the mill types who will upgrade when Intel tells them to. Secondarily they then put their own branded motherboards in a better light so they get that revenue stream ticked up a bit, when the enthusiasts pretty much stop buying their high end cpu's. They think that's a win in the end for them and carries them in the best way through the "strong AMD" bad times which they figure they'll get back under control in 2005. Then they can release a more overclocker friendly chipset, get everyone happy again, and put the market back the way they want it.

    Yep corporate types really do plan for this sort of thing.

    If they wanted every enthusiast out there to choose AMD this time around, looks like they've succeeded. Good job Intel! (sarcasm)

    And you wonder why many of their top engineers are leaving the company? hehe Hint, it's not rocket science...
  • Pumpkinierre - Saturday, July 17, 2004 - link

    Dont understand why you wouldnt get the same SATA failure with the i875/865 when you overclock? The link must also increase in speed when the FSB is increased but I have'nt heard of SATA failures on these mobos with overclocking.
  • zShowtimez - Saturday, July 17, 2004 - link

    Never thought it would come to it but so far its lookin like my next rig will be AMD. Reply
  • Anemone - Friday, July 16, 2004 - link

    You know, in 4 months Nvidia will have the NF4 with Pci-e for a chip that genuinely performs.

    Oh, don't take this wrong, P4's perform too but you have to give them some oomph to get things moving on them. And if Intel is dead set on making this impossible, then why don't enthusiasts just switch? Since Pci-e can't be locked but only run in 'tolerable' specs, then you know you are stressing your peripherals, something that modern chipsets were supposed to have left behind over the past few years.

    Intel I guess didn't learn their lesson with RDRAM, and think that telling the user community how they want things done is acceptable.

    Personally I don't like that attitude. I don't care for what they consider calling a competitive price for a lower performing chip, and I think it's high time the user community gives them the same message it gave them over the memory issue, "goodbye until you clean up your act"

    For me, I think this about does it. We'll see if others feel the same.


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