You have to get into your BIOS, find Advanced Clock Calibration and then enable the 4th core from this setting. Overclocking your CPU, on the other hand, you would be adjusting the base clock (200 MHz @ stock) and/or the multiplier (15.5 @ stock). Note that after roughly 3.4 GHz, you'll probably be needing an aftermarket cooler and start adjusting vcore and the northbridge settings.
Remember, the speed plus the voltage of the CPU will determine the resulting temperature, so for higher OC levels, an aftermarket cooler is a must.
Well it's very difficult to give you advise because I don't know how ASRock mobo's work.I know that in a MSI mobo the unlock core feature is located in the Intellagent Tweaker settings(where you would go to O.C. the CPU and change voltages).It's basicly an on and off switch.You can turn it on and it will automactically try to unlock a core if it's possible.
Go back to the basics. Clear CMOS or reset defaults. Do not try to unlock the hidden core. Now, using the X3 as and X3, try your hand at overclocking.
Step 1: Disable all power saving features (C1E, Cool n' Quiet, etc)
Step 2: Manually configure your RAM to the specs on the sticker affixed to the side of the RAM
Step 3: Raise your base clock by 5 MHz. Save and Exit. If Windows loads, go back into BIOS and raise the bclk by 5 MHz again. Repeat until Windows does not load.
Step 4: Now that Windows will not load, drop the bclk by 1 MHz until you can get back into Windows
Step 5: Download, install, and run Prime95. Run the Blend test for 3-4 hours, or as long as you can. Most of the pros on this forum run Prime95 for 24 hours before really declaring stability.
If you can get through this, your CPU overclocks just fine. On the other hand, if your attempts to OC were with the 4th core enabled, then chances are the 4th core is just defective.
Probably won't need to adjust voltage yet. Increasing the FSB up to the point of failure will likely get to ~215-220 MHz. At this point, the stock cooler can handle this, but it isn't a significant gain. I'm just trying to help determine if the CPU can be OC'ed or not. Besides, the OP still hasn't mentioned whether or not an aftermarket cooler is being used, so since I don't know that, I don't want to recommend raising the voltage yet.
Well I found the exact instructions provided from ASRock themselves on how to use the core unlocker feature.If it doesn't work then maybe he has a defective mobo.Or like I said before maybe it just needs a new BIOS version.