It depends on the processor. Many of the older chips cannot be updated. You could have a look around the freaktab forum for your processor type and see if anyone has developed a firmware. But be very aware that you could brick your box as even if the processor type is the same the firmware may be incompatible. Do you actually need to update your box anyway? I have droix (droidbox) machines i support for friends running Android 4.4.2 and they are perfectly happy with them.