[U-Boot] Die id?

Hi, All! I have a question about serial No. and Die ID. I've found this info: http://www.mail-archive.com/u-boot@lists.denx.de/msg10042.html

Can you tell me please what is Die ID? I need some serial No, which could be used as unique ID of device built on OMAP3 processor. Is this possible to realize with Die ID?

Thank you.