If system displays CMOS BATTERY STATE LOW or if the system displays CMOS CHECKSUM ERROR then most likely the CMOS battery or R.T.C chip (Real Time Clock) is running low. On the new motherboards we have the R.T.C chip is soldered on board and therefore it is not replacable. If the problem like this occurs with new motherboard then you will need to replace the motherboard. Most of the early 486 motherboards had the CMOS battery and if the CMOS battery ran low on those boards we could send the customer external battery.