Im not sure if its normal or not, but from my experience, I have a Asus M5A97 w a 8150 an a Saber R2.0 w a 8320, both are on the latest bios, when only using 2 ram sticks of 8GB I could only disable 2 cores at a time. Fill all 4 ram slots w 16GB an I was then able to shut down each core individually. I thought it was odd, but I have tested on both boards an got same results. Idk bout disabling for higher performance, never tried. With that board an cpu, though for increase OC it. Get a cooler. For best results with that chip, go for a H60-H100 depending on your case an you will notice an increase in performance.