SPL is similar to a BIOS in a computer and can be flashed and updated.
The version format of SPL looks like this:
x.xx.xxxx (Example: 2.17.0001)
If the SPL ends with 0000 it is a G3 Chip and ending with 0001 shows it is a G4 Chip.
Publication No. WO/2009/153387 Published on Dec. 23, Assigned to Nokia Siemens Networks for Software Loading Method, Apparatus (Finnish Inventors)
Dec 24, 2009; GENEVA, Dec. 29 -- Markus Kivila and Jan-Erik Ekberg, both of Finland, have developed a software loading method and apparatus....