How do you overclock a AMD Athlon 64 3500+ venice in a GA-K8N-SLI motherboard?

AMD Athlon 64/A64 x2/Opteron and Sempron (S754) Overclocking

For A64 overclocking, the technique is slightly different. There are some things to keep in mind.

-You can run memory dividers without the penalty of performance loss.
-The HTT Bus speed must never exceed 1000 MHz. It leads to instability. To amend this problem drop the HTT Multi.

Step1.
Restart your computer and tap delete to get into BIOS. Go to the frequency control options. The first step is to find out how far you can push your CPU. This means putting your ram on a divider so it doesn’t restrict the CPU’s overclock. Set the lowest divider possible, which generally is 100 (1:2), but it maybe 133 (2:3).
Step 2.
Lower your HTT Multi. The name of this differs in most bios’. Generally is called LDT Multi. If you have a Socket 754 system drop it down to 3, if you have a Socket 939 system drop it down to 4.

Step 3.
Increase the HTT (FSB). This maybe called FSB, Internal clock frequency or CPU Bus frequency in BIOS. Rise this to 210. Press ESC then save and exit.

Step 4.
Has your system successfully booted into windows? If so go back to bios and repeat step 3. Carry on like so, keeping in mind the HTT Bus Frequency shouldn’t go over 800 (S754) or 1000 (S939).

i.e. - on a socket 754 system you have hit 270 FSB on a 3x HTT/LDT Multi. Your HTT Bus Frequency is now 810 MHz and is over the stable limit. Drop the HTT/LDT Multi to 2x.

I.e.2- on a socket 939 system you have hit 250 FSB on a 4x HTT/LDT Multi. You have hit 1000 MHz bus frequency. Drop the multi to 3x.

Carry on like so till you notice instability in windows.

Step 5.
Okay, windows is unstable. Go back into BIOS, and increase the Vcore by 0.025V. Press ESC and save and exit. Does it feel more stable? If so run SuperPI 8M test. If you get any errors or lockups it is still unstable. If it still is unstable increase the voltage by another 0.025V and try again.

Do note that increasing voltage on the CPU can reduce the lifespan of it, and overvolting it to a certain degree will kill it. Here are the general limits for each A64 core.

Newcastle- 1.65V Air Cooling max/1.75V watercooling/1.8V Phase Change
Clawhammer- 1.65V Air Cooling max/1.75V watercooling/1.8V Phase Change
Winchester- 1.6V Air Cooling max/1.7V Watercooling/1.75V Phase Change
Venice- 1.6V Air Cooling max/1.7V Watercooling/1.75V Phase Change
SanDiego- 1.6V Air Cooling max/1.7V Watercooling/1.75V Phase Change

Like I said in the beginning I will not take responsibility for any damage done to your CPU. There are the odd weak chips around that may not take very high volts.

Also when you increase voltage keep a watch on temperatures. More Volts=Higher Temps.

Step 6.
So you have reached the point where your system is overclocked to the extent that it is unstable regardless of voltage. Go back into the BIOS and drop the HTT (FSB) by about 10 and save settings.

E.g. - A Hypothetical AMD Athlon 64 3000 Venice is unstable at 290*9 (2610 MHz) at 1.6V. I go into BIOS and drop HTT/FSB to 280 and try again.

Is it stable? Run OCCT for 30 minutes. Keep a watch on your temperatures during the test. I would suggest you see that temperatures are below 60*c fully loaded for socket 754 systems and 55*c for Socket 939 systems.
Is it failing OCCT? If so drop the HTT by 10 again and try once more.

Continuing step 6 till it is OCCT stable you have now safely overclocked your CPU.

n.b- To ensure that your system is stable use prime95 and run the small FFP test for an hour followed by the blend test for another hour.

As a final touch validate and publish your overclock. An example of an overclocked A64 validation here.