This module replaces the Dallas 12887 and 1287 Real Time Clock (RTC) chips that are used in many old computers. Especially old PCs. The problem with the original chips is that once the battery is dead you must replace the whole chip. You cant just replace the battery like you can in new computers. This module solves that issue and allows you to replace the original RTC chip with a module that has access to the battery. In this case, a CR1220 Battery, that you can chan ge whenever needed. You no longer have to risk damaging your classic computer in order to change a chip just to replace a battery.