More core voltage makes overclock less stable, why?

At the weekend I built my brother a 50% new PC as his old MB died. Specs are:
Athlon X3 440 3GHz Unlocked 4th core and L3 Cache now Phenom B40 3.35GHz
AsRock N68C-S UCC GeForce 7025 Socket AM2+ Motherboard (cheapest board I could get)
When overclocking I found that any increase in core voltage more than one notch above stock made it unstable (Prime 95 would crash in 3-10 minutes) is this because of the cheap motherboard unstable extra core or cache or something else? Temps are fine Prime can't push it past 50C and it was a very hot day.
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More about more core voltage makes overclock stable
  1. Can you give a little more info? What exactly did you do to overclock? What did you change? FSB? Ratios? Did you unlock the 4th core?
    FSB - you might need to raise NB voltage or it could be that the RAM is now too OCed and you need to either lower RAM ratio or increase RAM timings
    Unlocked core - might be unusable
  2. wolfram23 said:
    Can you give a little more info? What exactly did you do to overclock? What did you change? FSB? Ratios? Did you unlock the 4th core?
    FSB - you might need to raise NB voltage or it could be that the RAM is now too OCed and you need to either lower RAM ratio or increase RAM timings
    Unlocked core - might be unusable

    I raised the FSB to 224 which is stable but not above (set to async with PCIe) and unlocked a 4th core and L3 cache. Its not the RAM I lowered the multiplier and even tried it as low as it would go. I didn't try the NB voltage though. If I raise the core voltage above 1.4V its no longer stable even at the 3.35GHz.
  3. I just realised the motherboard only supports processors up to 95W and unlocking the cores may have pushed it to 125W or even 145W as its C2 and a C2 955 is 3.2GHz 125W or a C2 965 3.4GHz is 145W. Do you think this is linked to the problem and should I lock a core?
  4. simon12 said:
    I just realised the motherboard only supports processors up to 95W and unlocking the cores may have pushed it to 125W or even 145W as its C2 and a C2 955 is 3.2GHz 125W or a C2 965 3.4GHz is 145W. Do you think this is linked to the problem and should I lock a core?

    Imo, you answered your own question. The power circuitry is not strong enough to allow any higher stable 'current' draw.
  5. notty22 said:
    Imo, you answered your own question. The power circuitry is not strong enough to allow any higher stable 'current' draw.

    Do you think its dangerous to keep running it as it is
  6. As is, your system is not stable. You said so.

    All hardware risks aside, Is your data - all the contents of your hard drive - worth running on a stable system? If no, just keep running the way it is.
  7. the system is stable as it is but not if I increase the voltage
  8. Well if it's stable, why would you want to overvolt it? If you only want to add more voltage because you're also increasing the frequency but it won't work at that frequency, then it seems to be a motherboard limitation.

    If it's running fine, temps are fine, and it's stable, then it's not unsafe, but any overclocking will shorten the CPU life... how much? Don't know. But CPUs can easily last 10 years at stock.
  9. Thanks for the advice, my brother tried locking 1 core (still with L3 cache enabled) and can now over volt to get a stable 3.7GHz. I will start a new thread asking which is better 3.3GHz 4 core or 3.7GHz 3 core.
  10. In gaming the 3.7ghz 3 core will generally be better
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