if your going to reset the PRAM, to see if it helps, you should also reset the SMC.
resetting PRAM does not reset SMC. SMC mostly has to do with fan speeds, power lights, charging lights, sleep and wake issues.
I've seen a lot of geniuses help people with their macs and they always reset the PRAM in the store but
I've never seen a genius reset the SMC
maybe its because PRAM is something that came with the old POWERMAC and earlier?? and SMC was introduced in intel macs?? heh
intel macs have PRAM and SMC
apple says that resetting the SMC may help with :
System performance
The computer is running unusually slowly although it is not experiencing abnormally high CPU utilization.
Application icons may "bounce" in the Dock for an extended amount of time when launched.
Applications may not function correctly or may stop responding after being opened.
guess / speculation section
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i went to the genius. and asked them about our mac book pro 2011. he checked it, and he did the speech about rebooting it once in a while and not having too many windows open. he told us that Yosemite uses more ram then mavericks.
and he recommended us to get 8 gigs of ram.
it looks like to me, and i read it somewhere, that by default Yosemite likes to take all available ram and mark it as used, to make the system snappier.
your experience with the macbook air could just be because you have Yosemite running on a 4 gig machine
i think the genius was a little wrong. Yosemite just likes to use a lot of ram as a cache. and its the wired ram that can't be touched. what the genius said was with one finder window open the mac was still using swap space and was using like 3.8 gigs of 4 or something like that. and the memory was being compressed.
another thing the genius should of said that he didn't is that as long as the graphic on the bottom that shows memory pressure is low and it is green then your ram is fine and you don't need more ram
since the ram was upgradable in my brother's macbook pro , i just went ahead and bought 8 gigs anyway
feedback about last visit @ apple store section
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it kind of bums me that apple has IOS diagnostics that analyzes your crash logs and console logs, but when i asked the genius about it he said they have nothing for checking your mac. i know they have special mac diagnostics in the store, but when i told them i already ran apple hardware test, they said their special apple store hardware test did nothing more then what we already tried.
i asked them if they had anything to read or analyze the console logs they said no.
they didn't even have anything in store to check the hard disk.
