DDR800 on DDR667 Board - Can I overclock it to 800?

I picked up a Corsair 4gb (2x2gb) XMS2 DDR2-800 set today. My board is an XFX with the nVidia 610i chipset (two DIMMs), and it supports up to DDR2-667. The ram auto-tuned to 667 when I booted up, and it runs Vista 64 and UT3 better than my 2gb 667 stick did, but I'd love to get it "overclocked" to stock speed. The stickers on the ram say a timing of 4-4-4-12 800mhz, and they're defaulting to 5-4-4-14 at 667. My processor isn't overclocked or anything, just a Pentium Dual-Core E2200 with 800mhz fsb.

To get the ram to 800mhz, can I just change the timings, or do I need to increase voltage? How much risk is there in this kind of adjustment?
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  1. You have an Nvidia chipset, so there should be an option to run the memory unlinked. Unlink the ram, then increase it to 800mhz.

    If that does not work, then you'll have to increase the bus speed. The bus speed should be 200, the QDR(FSB) is 800. You can incrementally increase the QDR slowly like 10-20mhz. That should also increase your RAM speed if it is currently linked together.
  2. Alright, I put the QDR to 800 and the bus speed to 200. That gave me a generic instability message at POST. What seems to work fine is setting BOTH to 800. I've also got my voltage increased to 2.0, which is the max that my BIOS will let me go. The sticks say they're rated 2.10.

    Only thing that bothers me now is that my Vista Experience Index went from 4.7 for ram to 4.8. Shouldn't it be a bit higher?
  3. I think you are confusing Bus speed with memory and QDR. At 200mhz bus speed, your QDR will be 800mhz, but your memory is acutally running at 667mhz.

    If you got instability because you set your memory to 200mhz, in effect it is running at 100mhz * 2. When you set it to 800mhz QDR and 800mhz RAM, that is the correct speed, I wanted to you do.

    Regardless It's good that you are running at 800mhz ram now.

    Don't put too much value into Vista index. CPU probably is the most defining factor when it comes to Vista index. My memory is 800mhz 5-4-4-15 2T and it is 5.9, but I have a fast processor.
  4. Hmmm. Well, come Christmas, I'll be replacing the E2200 with a Core 2 Duo 4700, so I guess that will help. I'm going to try setting my timings back to auto, see what that does with the new speed settings.
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