The Yellow Light of Death is a way for your PS3 to tell you that it's crapped out on you, and you're going to have to send it back to Sony. it can mean any kind of hardware failure. As far as frequency goes,due to a fault with the thermal paste that was used on the original PS3 that dried up causing it to over heat. But it can also happen on any model for any other reason as well
Typically to fix it, people replace the old thermal paste with: Artic 5 thermal paste, or they also have the system "REFLOWED"
BOB: sup man my ps3 is acting weird man when I turn it on I don't see nothing man, I think its got the YLOD
STEVEO: dude its probably that crappy thermal paste that dried up, go buy some artic 5 thermal paste from ebay and fix that beast