With the PS3 power switch in the off position, turn power switch back on while holding down Eject button. This "fan test" mode allows you to clean out the Dustmites inside the PS3. It works for Models CECHG and higher. (Note that a plugged in PS3 Slim does not have a power switch at all and is always in standby).
The following requires the power switch in the back to be on...
Hold Power button down for 6 seconds (while PS3 is on): turns off PS3.
Hold Eject button down for 6 seconds (while PS3 is on): force disc to eject.
Hold Eject button down for 12 seconds (while PS3 is on): reset Blu-ray.
Hold Power button down for two beeps (while PS3 is off): Reset video to lowest settings.
Hold Power button down for three beeps (while PS3 is off): Enter PS3 diagnostic mode (repeat procedure twice)
Hold PS button down on controller for 10 seconds: Turns off Sixaxis or Dualshock 3.
The PS3 can enter a special "Service Mode". When it does the bottom right hand corner of the screen has a red translucent rectangle with the words "Playstation 3. Factory/Service Mode" inside of the rectangle.
It is rumored that by plugging a special JIG in the USB port, the PS3 is triggered into Service Mode the next time it boots up. This special mode then accepts firmware code loaded in from the USB port, and allows reflashing the firmware chip.
Each PS3 has a special 512KB EEPROM chip on the motherboard using a SPI Serial Interface Renasas chip.
Serial Number: HN58X2504TIE
Description: PS3 EEPROM chip