Long-term settings for printers and other embedded devices are stored in non-volatile memory ([NVRAM](https://en.wikipedia.org/wiki/Non-volatile\_random-access\_memory)) which is traditionally implemented either as [EEPROM](https://en.wikipedia.org/wiki/EEPROM) or as [flash memory](https://en.wikipedia.org/wiki/Flash\_memory). Both components have a limited lifetime. Today, vendors of flash memory guarantee about 100,000 rewrites before any write errors may occur.
For a practical test to destroy NVRAM write functionality one can continuously set the long-term value for the number of copies with different values for `X`:
Usually, before stop allowing writing anymore NVRAM parameters are fixed to the factory default value and all variables could still be changed for the current print job using the `@PJL SET...` command.
For PostScript, one needs to find an entry in the currentsystemparams dictionary which survives a reboot (and therefore must be stored in some kind of NVRAM). A good candidate would be a PostScript password.\
**More information about these techniques can be found in** [**http://hacking-printers.net/wiki/index.php/Physical\_damage**](http://hacking-printers.net/wiki/index.php/Physical\_damage)
