Hello, I had wished to give you a bit of advice on Overclock of the A8-3870K. I have had this chip since release paired with the ASUS A75 V-EVO motherboard and I have reached decent overclock. 3.5Ghz was possible on all of the 3870K tested by myself and pals. I myself have reached 3.8Ghz but this was not stable for regular use. I found 3.7Ghz & 3.6Ghz voltages leading to higher temps than I liked so have been happy on 3.5Ghz and 900Mhz GPU for a while now. The key to an easier overclock is little more than the correct knowledge on Voltage & the right Motherboard.
The following voltages have been used by myself for over a year and half without problem, my PC is not left on 24/7 but used daily so it gets an easy 12hrs a day. Please note my voltage descriptions below are based on the ASUS terminology, this will change on other boards so understand the voltages I refer to below and then make the changes in your own BIOS.
3.5Ghz is easy using the below;
CPU V - 1.53750V
VDDNB (Northbridge) - 1.3250V
SB1.1V - 1.15000V
1.1VSB - 1.20000V
APU1.2V - 1.30000V
VDDA - 2.50000V
In my experience the 3870K is a hardy little chip, this said CPU voltages above 1.59v shouldn't be applied for 24/7 use. I have been using Coolermaster Hyper 212+ as my cooler and it has done the job. After replacing the thermal paste after 1 year (key) I now have idle temps of 30c and load temps of 49c (5hrs on Battlefield 4). I hope the numbers above help you out. Write me any questions, cheers.