New PSU Slow CPU (new psu has an 8 pin cpu power connector the old one had 4 pins)

Core i5 3570K (3.4 Ghz) C.P.U
Biostar TZ77B Mobo
8 GB Corsair Vengeance
Asus HD 7850 G.P.U
Cooler Master 460W (old)-Apevia 700W (new)

So I built this PC about a month ago and everything went smoothly and all the components operated properly. When I first built the system my 460W PSU only had a four pin connector for the CPU power (mobo had eight pin). I read the manual for the mobo and it had instructions for both configurations so I knew I could use the four pin.

I needed a new case and I figured I'd update the PSU at the same time so I acquired an Apevia 700W (eight pin CPU power). The rebuild went smoothly, didn't hit or mess up anything.

Upon booting up the boot screen came up saying everything it usually said adding "CPU has been changed. Please re-enter CPU settings in the CMOS setup and remember to save before quit!"

I figured O.K. the CMOS and system configured itself to a different power profile for the CPU and interpreted the new power source as a new CPU so I did what it asked, I went in the UEFI bios and pushed F3 for default settings, saved and restart.

Now PC boots without a message about CPU change but its really slow. Slowly (very slowly) I get into windows and run CPU-Z and my CPU is at 1.6 Ghz (not 3.4) so I shut down.

On my laptop I researched forums for hours finding similar circumstance (less the 8 pin to 4pin change) and I concluded I needed to reset CMOS. I reset CMOS by removing the battery in the mobo and shorting for a few seconds, reset, went into UEFI bios and verified it had reset, set to default settings adjusted the time and date, saved and reset.

After booting I find my CPU is still running at less than half the speed it was just yesterday with the oter PSU.

I'm convinced the power supply is working fine because everything else (main power, sata, optical drive and fans) operate exactly as expected.

The only other thing I changed beside PSU and case is I added a couple case fans to a molex connector. Also everything runs perfect on the system its just as if I installed a much slower CPU.

Please help.
Thank you!!!!!!
7 answers Last reply
More about psu slow cpu psu pin cpu power connector pins
  1. CPU-Z and my CPU is at 1.6 Ghz maybe run at idle ???

    that's normal
  2. Called Intel Speed Step.
    Further to that you upgraded from a bad PSU to a worse, Apevia is on top of all avoid lists!
  3. rolli59 said:
    Called Intel Speed Step.
    Further to that you upgraded from a bad PSU to a worse, Apevia is on top of all avoid lists!

    What should I do? replace PSU and problem solved?
  4. You have not confirmed you are taking the speed reading on idle. Changing PSU would not cause the CPU changed message so your problem may be somewhere else.
  5. Problem solved. It turned out to be a corrupted driver for the sata dock I installed with the new case slowing my PC to a crawl at start up. The slow start up (from driver software) coupled with "warning cpu has changed" message led me to believe it was a hardware problem with the PSU. (face palm)

    Thank you for the advice though because the realization that my cpu was likely in idle mode (and not under powered) led me to the final resolution.

    Also I have been using cheap PSU's with a false sense of impunity for years. Even though this didn't turn out to be the problem it got me thinking and I will be buying a new PSU.

    Any suggestions, I would like to have at least one PCI 6pin plus a 6pin+2 at a minimum of 700W for the best price possible.
  6. I still don't know what to make of the "CPU has changed" message but resetting CMOS removed the error, also I ran 3d mark and monitered my CPU at 3.7 GHz so that's all good.
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