Only the current BIOS settings that the computer has been using are cleared, not the main settings, which are permanently placed into flash memory when the BIOS chip is flashed. (The BIOS can be reflashed with an updated file.) Unlike RAM memory, flash memory holds data without being powered. When the PC starts up and tries to access the BIOS settings, it finds none if the BIOS has been cleared by the reset jumper setting and it makes the BIOS copy the default settings from the flash memory into the RAM memory that is kept alive by the CMOS/BIOS battery. By placing the jumper over the two pins that allow the CMOS battery to power the CMOS chip that holds the settings, customised settings are retained. Removing the CMOS battery also removes the current settings. Any customised settings are lost. The CMOS/BIOS battery is shown on the left.Bios Jumper placed on mainboard
Only the current BIOS settings that the computer has been using are cleared, not the main settings, which are permanently placed into flash memory when the BIOS chip is flashed. (The BIOS can be reflashed with an updated file.) Unlike RAM memory, flash memory holds data without being powered. When the PC starts up and tries to access the BIOS settings, it finds none if the BIOS has been cleared by the reset jumper setting and it makes the BIOS copy the default settings from the flash memory into the RAM memory that is kept alive by the CMOS/BIOS battery. By placing the jumper over the two pins that allow the CMOS battery to power the CMOS chip that holds the settings, customised settings are retained. Removing the CMOS battery also removes the current settings. Any customised settings are lost. The CMOS/BIOS battery is shown on the left.