Hello! My CPU fans for proc.A are near-constantly capped at 300rpm(system minimum), no matter how damn fast the B-fans spin to compensate. I have: Kept it clean inside. Kept CPU settings on Highest, as usual, but tried Reduced/Auto Repaired permissions Reset the PRAM Reset the PMU Booted into single-user mode Reinstalled Leopard Obtained & ran Service Diagnostic CD and passed all tests Re-calibrated the CPU's only to notice the speeds now hover around 400rpm now... What more can I possibly try? I don't believe a re-seating of CPU's is in order. They work great. All my fans & temperature sensors passed their diagnostics tests, too. I am very irritated by the noise of 2/4 fans overcompensating and getting very loud, from 2000rm-4000rpm, and hey, my Mac is screwed up, and I really need to fix this. It's the G5 in my sig. Mid-2004. Thank you all for your brains, experience & consideration.