THIS IS A NEW CMOS BIOS BATTERY THE CMOS BIOS BATTERY IS CALLED A REAL TIME CLOCK BATTERY FOR THE REASON THAT IT SERVES ONLY THE PURPOSE OF KEEPING THE CMOS FIRMWARE ACTIVE DURING THE NOTEBOOK'S SHUT DOWN (NON USAGE OF THE NOTEBOOK). THIS TINY BATTERY WILL POWER THE UPDATED FEATURES OF THE CMOS SO THAT BOOT SEQUENCE SETTINGS WILL BE CONSISTENT, AND WILL KEEP A CONSTANT DATE AND TIME ON THE NEXT BOOT UP. YOU NORMALLY WILL NEED TO REPLACE THE CMOS BATTERY WHEN THE NOTEBOOK HAS A CORRUPT CMOS ERROR FLASHING ON THE SCREEN AT START UP. ANOTHER INDICATOR IS THAT THE DATE AND TIME SETTINGS ARE NO LONGER ACCURATE. THIS TINY CMOS BATTERY SHOULD NOT BE CONFUSED WITH THE MAIN LITHIUM ION BATTERY THAT FULLY POWERS YOUR NOTEBOOK WHEN IT'S NOT DEPENDING ON THE AC/DC ADAPTER CHARGER THAT CONNECTS TO YOUR HOUSEHOLD CURRENT SOURCE. THIS BATTERY SUITS THE TOSHIBA PORTEGE M200 SERIES MODELS.