Before you read please take a look at this thread:
I've spent an hour talking today to Intel's Customer Support. By the way, it took them less then a minute to already have someone talking to me. This is how it should be done, Asrock.


Moorthy: Hello. Thank you for using the Intel Customer Chat Support service. We are glad to be of service. How may I help you?
Me: Hello there
Moorthy: Hello
Moorthy: How may I assist you today?
Me: to keep the situation short, the problem i'm experiencing is that my i5 2500k cpu is behaving abnormaly
Me: in a sense that it doesnt want to boot at specific multipliers
Moorthy: May I know the exact issue you are facing with the processor?
Me: yes, I have an Asrock z68 Extreme 3 Gen3 motherboard.
Moorthy: I see
Me: When i choose cpu multiplier in a range of x43 to x46 included
Me: the system will not POST
Me: but, interestengly, i am able to boot at x47 and x48
Me: and x42 and below respectively
Moorthy: I understand that there is no display if the clock multiplier is set between 43-46.
Me: Yes, the motherboard debug code is 70, which stands for South Bridge DXE Initialization
Me: and trust me on this, i've tried every setting available in bios but to no avail. I have a stable system at x47 running at fixed votlages and it can run prime95 for 10 hours
Moorthy: Okay.
Moorthy: I see.
Me: But there's just no way i can boot up in the above mentioned ranges
Moorthy: Please be online for 3 minutes while check for the details.
Me: Ok
Me: For more info I have a 750w PSU 85+ certified and a GTX570 on board
Me: Furthermore overclocking profile presets on my motherboard are available for 4.2, 4.4, 4.6 and 4.8 Ghz, and only 4.4 and 4.6 dont work. Trying manual settings obviously didnt help
Moorthy: Thank you for being online.
Moorthy: Thank you for the additional information.
Moorthy: I do require some more time. Please be online while check the details.
Me: Sure
Moorthy: Thank you for being online.
Moorthy: this is an unlocked processor.
Me: Yes, I know that and what it means
Moorthy: As per our records the maximum turbo frequency is 3.7 GHz.
Moorthy: However, when the processor is over clocked, the other parameters like the RAM voltage, etc needs to be considered.
Moorthy: As per your information, the processor is working is higher multiplier.
Moorthy: This issue could be with the BIOS, since the multiplier is set in the BIOS.
Me: Can I add more interesting information please
Moorthy: Yes, please.
Me: In my UEFI, there's an option called "Advanced Turbo 50
Me: which boots my PC at 4.8ghz and 1.43v
Me: and its stable
Me: The monitoring software tells me that the only thing changed were the core voltage and the igpu voltage
Me: Now the very interesting fact, is that if i *reboot* my system and load the bios and enter x46 and all my voltages in, save & exit, i am then able to run it just perfectly fine!
Me: but when i *shut down* the system, it will not perform a cold boot on x46 multiplier
Me: So apparently i can run it fine at x46, and I've done a complete 24 hour test on Prime95 and everything is great. But as soon as i shut down the computer, it will not start
Moorthy: I see
Me: This is what is killing me :)
Moorthy: This finding is indicating that the BIOS is not saving the details on complete shut down.
Me: Yes, I thought so too
Me: But how come its only for specific multipliers?
Me: I can save an x47 profile and shutdown and start with no trouble
Moorthy: Or it could be that the when the system is running the data is saved, however, after cold boot the information is lost.
Moorthy: I see.
Me: Maybe
Me: Its because there is a profile for x46 in the bios?
Me: But that wouldnt explain why I cant boot at x45 either
Moorthy: I would request you to check with motherboard vendor too.
Me: I have to say they are exceptionally quiet
Moorthy: It seems like that the certain profile are being saved and some are not.
Me: But i just want to clarify: this is not a CPU issue?
Moorthy: However, from your end you check if there is any issue with the processor.
Moorthy: Please refer the below link.
Me: Ok
Moorthy: Processors — What is the Intel® Processor Diagnostic Tool?
Moorthy: This utility does a complete functional testing of the processor.
Moorthy: There an test called Base frequency test.
Moorthy: I would recommend you test the processor is default settings of the BIOS.
Moorthy: Check if there is any reported issue for frequency etc.
Me: Right, for more information, after a restart I am also able to boot with x44 and x45 multipliers
Moorthy: I think the possible reason for this issue could be with the BIOS.
Me: I was leaning towards this also
Me: But now I'm more sure
Moorthy: I believe, that once you configure the multiplier, it would saved in the BIOS as profile.
Moorthy: After a shut down either is conflict in the saved profile and default profile.
Moorthy: To isolate the issue, you can try save all the profile.
Me: Its very tricky because my x47 profile is saved, since it is stable and I'm able to boot with it, and I can load it and forget about it. The PC will shutdown and power on just fine. Its just weird that it will not work with multipliers below
Moorthy: to keep you informed. Using overl****ing requires additional consideration of the RAM, PSU etc.
Me: Yes I'm aware
Moorthy: We only recommend you to use it under normal condition.
Me: I doubt its the RAM and PSU because I can coldboot and be stable at x42, with same voltages to ram and same timings
Moorthy: However, you can go ahead overclock the processor, but the other factors needs to be considered.
Me: and i can also boot with the same configuration at x47, so I think it eliminates the problem
Moorthy: I would suggest you to check with motherboard vendor, if the multiplier requires an additional changes to be made.
Moorthy: To test your processor, I have provide you with our testing utility.
Me: Thank you, I will do everything you've suggested. I have to say I'm very pleased with your help and Intel's customer service
Moorthy: It is my pleasure assisting you.
Me: Can you advice me on one more thing please: would you recommend me on what vcore could be considered "safe" for everyday use? I know the risks, but just to avoid the degradation, is there something I must be aware of ?
Me: I understand degradation can occur at any voltage and its specific to my chip, but I'm wondering if Intel has some safety "recommendations"
Moorthy: please go through the below link.
Moorthy: Intel® Core
Moorthy: The above link contains the details of the processor normal working conditions.
Moorthy: Please note that running desktop board components beyond their nominal values adds additional thermal considerations to the overall system and adequate cooling should be employed to ensure stable system operation
Me: Could i pleas rephrase
Me: Is it true, that running a CPU with a high-end heatsink and below 1.4v will reduce the risk of degradation to a minimum?
Moorthy: when the processor temperature is below 72.6°C and maintained below this, it is fine.
Moorthy: However, running the processor above normal conditions, may result in degradation in the long run.
Moorthy: your processor is unlocked processor. It can used for fine tuning.
Moorthy: However, recommend it to be used below the normal conditions
Moorthy: Please refer the below link.
Moorthy: The above two link contains the complete details of the processor.
Moorthy: The supported frequency, thermal details etc.
Me: Ah yes, but its confusing because the maximum voltage mentioned is 1.52v
Me: and many have confused that anything less is safe
Moorthy: I understand your concern.
Moorthy: Please do go through the below link.
Moorthy: Intel Overclocking Guide
Me: Thank you very much for your information. Can i print our discussion for future reference when i talk to Asrock ?
Moorthy: When you end the chat, you would have an option to sending the chat transcript to your email address.
Moorthy: Please select the option.
Moorthy: Is there anything else that I can assist you with?
Me: No, thank you, you've been very helpful
Moorthy: You are welcome.
Moorthy: Thank you for using Intel's live chat. If you are satisfied with our support, please score items with 5 in the online survey that will be shown once you close this chat window. We value your feedback and we will use it to improve our services.
Me: Goodbye ;)

I will just add that I've run the diagnostics tool and my CPU is in excellent condition.
I demand Asrock to fix this asap.