I would not run a 10900K off of one CPU 8pin. The chip can draw over 200watts while stress testing. Use both. If you are going to use only one, I would not OC at all (not even MCE) until you get the second plugged in. These chips can draw a lot of juice when pushing AVX instructions, and some games now use AVX in one form or another. I wouldn't want to steadily pull 220watts from a single 8pin. The cable can probably handle it, but why take that risk?