NOR (SysCfg)

SysCfg is a section of the S5L NOR (or NAND) that stores vital information such as your device's model number and serial number.

Importance
Although it is very important to have this, as iBoot needs to populate the DeviceTree with this information, it appears that some people have been able to overwrite their NOR with garbage and somehow got this data back after a restore. In the case of the iPod touch 2G, this section of NOR seems to be read-only by default.

This varies by device - on other devices, if you alter SysCfg, the device may be bricked.