...just today i realised one thing: suddenly all my RAM starts running down like a countdown to around 18MB . and my computer becomes slow and irresponsive. i have 8GB of RAM. i try the "purge" command, and for a few minutes free RAM is like 5GB...then starts counting down again to about 18MB. i tried restart, shut down. nothing's working and i'm very sad. i love my iMac but it's started acting strangely. did some googling and nothing useful... can someone help me please? current inactive RAM: about 6GB...why that much?