I bought a delided 3570k a while back (maybe 18 months)
Noticed recently at stock clocks one core was idling at 60c. With an H50 cooler. I had run the cpu at stack for a least 6 months. Nothing crazy before that.
Rig was dusty so I blew it out and it wouldn't boot when I went to start it back up. Tried all the usual stuff, one stick of ram, removed cmos battery. The board was giving me an error that manual says is related to the L2 cache.
I had a celeron so I tried it...