I did some tests on resetting the PRAM/NVRAM in different known-good macs and was surprised to see varying results: What I did is to adjust sound volume and screen brightness in OS X to minimum and then shut down the machine and reset the PRAM: in one iMac the screen brighness wasn't reset, that is: it remained at minimum after restarting (even during startup). Yet the sound volume was reset to a medium level (startup chime and then in OS X). On an macbook: I did the same, but the PRAM reset didn't reset neither the sound volume nor the screen brightness, they remained at minimum. On another macbook: I removed the battery and the power adapter and these settings were reset to an intermediate value. So my doubt is: where does a mac save these settings other than the PRAM (now called NVRAM)? How can the screen brightness be kept at minimum after resetting the NVRAM? where's this saved? in the SMC?