I bought an IBM Model M keyboard from Ebay with the part number 1391401. I have an ASRock Extreme3 Gen3 motherboard with an i5 2500k cpu. At stock cpu clock 3.3ghz, the IBM Model M has no response on the native ps/2 port on my motherboard. I took some advice from a thread I found on this forum to overclock my cpu, and my IBM Model M finally comes to life at a cpu overclock of 4.3ghz.
I buy a "Blue Cube" adapter from cyberguys because I am a little suspect on the lifespan of my cpu leaving the overclock that high. With my Model M plugged into the blue cube adapter, my motherboard detects the new usb device and installs drivers but the keyboard never works. I have restarted multiple times and I have tried all of the usb ports on my motherboard and my case. I have tried this blue cube adapter on a 1999 ps/2 Gateway keyboard and that works fine, but for some reason it will not work with my Model M.