What is FAN IN and FAN OUT in Digital Electronics.?

fan in refers to the number of input a chip can receive input from and not over load it. fan out is similar but the number of out put devices that a chip can drive with out over load of the current requirements of the chip.

What speed is the hard drive? It's recommended that you only put in a 5400rpm disk, faster disks generate more heat, which triggers the fans thermostat to make it spin faster. It's worse in the hot weather. If you want to be certain swap back to the old disk to see if the fan is still fast... be careful though, doing this will mean you can't put your new disk back in without formatting it. Back up everything first. If after swapping the disk back the fan still throttles, try the fan cleaning routine. This is triggered by holding the eject button down whilst turning the PS3 on using the switch on the back of the machine. If all else fails try calling Sony technical support.