Chosen Solution
I’ve been refurbishing 2011 27” iMacs for a while now and I’ve come across 2 logic boards with a strange symptom. Both of them cause the GPU to run at 100MHz instead of the normal 680MHz. Everything else on these boards functions properly. I’m thinking there’s a voltge or current problem but I don’t know what to check. Any clues?
@notenufgarage - I think you damaged one of the two ferrite beads near the sensor connectors. Review this question: GPU/CPU working at 50%
