Did you re-use your old PSU in your new rig? was it really old? I wouldn't reuse old PSUs. PSUs are like batteries, they have a life cycle, their longevity is limited.

My PSU is only a couple of years old, EVGA 550W and my new setup needs a lot less than that. I could go with 350W and still be fine. These new CPUs and video cards are amazing.

"a couple of years"? That could be too many years, depending on the quality of components used in the PSU, and the total working hours it has logged already. PSUs loose maximum capacity safeties with the passing of life, and enduring heat. They may lose the ability to maintain stable power levels.

Just repüeating what I was told by a guy I kinew who really knew it better than I do. He ran very expensive rigs himself, and security-critical rigs for a company. He replaced PSUs every two years - prophylactically.

It may have been a spike that killed your mobo and GPU, maybe during the startup when you hit the on-button. Could be. If the PSu was too detoriated, it may have created an intiial starting spike too strong for the hardware to digest. There always is such a spike initially when switching on the power, but a PSU that is in good order should keep it below critical treshholds.

Also, the maximum output possible may suffer - maybe even signficantly - with growing age of a PSU. Its a wearing part. And many people underestimate the need fopr gpopod quality in tzheir PSU and stable power distribution.

All I mean to say is: it must not have been the PSU, but it could have been the PSU. If it has several years in its record already, I would not re-use it in a new system, its just a risk.