I found an IBM PC/AT (for spare parts for another recently acquired one) with a small card placed in between one power supply lead to the motherboard. It also has a lead clipped to the motherboard, presumably to insert modified clock frequency to the 286. On the board it says "Megahertz Corp (c) 1986 286-2 REV 4". The board bolts to the back of the chassis and has one button (reset) and two switches (6MHz-Turbo and rotary 8-9-10-11-12). Obviously this is meant to over clock the 286, with the rotary switch allowing increasing the clock frequency until the 286 fails. So, this suggests these questions: 1) Does this really work? I thought you couldn't over clock a true AT? (This particular motherboard is a "256/512 K System Board" with piggy-backed RAM chips. It has lots of "ECOs" on the pin side of the board. I don't know if my other one does, too. Note: ECO = Engineering Change Order.) 2) Would increasing the 286-6 to a 286-8,10,12 increase the frequency at which it could reliably run? I have a PGA 286-8, but I'm not sure there are faster PGA 286s? 3) Any software needed? (The ROMs appear to be the same as on my other machine.) Thanks for any information anyone can shed on this. Dave