Puzzled.

Since it's summer, I'm trying to scale back my overclock of my athlon 64 3500+.

Currently I am running a 2.7ghz OC (270x10) with a 166 divider, putting ram speed at 225. Also, cpu voltage is 1.58v. Memory is running at 2-3-2-5.

Here's where the problem comes in: When i try to decrease FSB to 260, my computer won't boot, even with the same voltages. However, I can get a stable boot at 1.55v, just not prime stable. Additionally, when i tried 237x11 boot with a 1:1 memory ratio, the boot failed. I have also tried a 1:1 memory ratio at 260mhz, but that also fails. When i run memtest for fsb=260 with same voltages and ram timings and dividers, it fails. BUT, when i run memtest with fsb=270 and same voltages as the last test, it passes. This confounds me.

If anyone has any ideas of what I should do, help would be much appreciated.

Thanks in advance

~JOW!

Hmm...I've seen this before, and its definetly a strange problem indeed. First off, you said you were running 1:1 at 260MHz? Thats pretty fast, especially for PC3200. I'm not surprised that that's failing.

Other than that...try going down in baby steps, like 1MHz at a time. When you hit a wall, go back one and burn in a bit, then try again.

Another option is to try a BIOS update that clears all your previous settings, which will take you back to stock. Then go up from there.

Hope this helps!

I used to be able to run 270fsb at a 1:1 ratio, but i can't anymore (not sure if it's the same problem with bios or if my ram has just deteriorated in quality). I'll try lowering it in baby steps, but in the end I'll probably end up doing a bios flash. Thanks for the input, anything else anyone suggests would also be greatly appreciated.

~JOW!

You may have to revert back to stock and reboot check the settings with CPUz or sandra. Start working your settings back up to where you had them. You may have to relax the memory timings to keep this form happening. The bios make adjustments behind the scenes to map frequencies and clocking to make the CPU and Ram respond correctly. I've seen this happen before and it's frustrating. My K7N Delta is really bad about this and hard to correct. I've also seen this on BFG mobos too make my OCZ ram not even run stock until I tweek it back to normal. It took several attempts to get my DDR500 to run 500 as 2.5-3-3-8 (OCZ stock). It's now been there for a while. A bad boot can kill these settings like after the rigs been off a long time or cold. I think this is also what people refer to as memory burn in where actually they are working the BIOS to get better timings. With a DFI, you have more control which may be the reason DFI is such a good board for overclocking.

Update: I did a bios flash and now am running 260x10 = 2.6 ghz, 166 divider. vcore = 1.536. Stable as ever.

Good to hear!

Great news ...!