Personal computer with cmos memory not having a separate battery

Abstract

A computer system which utilizes a CMOS memory/RTC and does not have a separate battery for powering the CMOS memory/RTC. A serial EEPROM is utilized to maintain the contents of the CMOS memory. When the computer is entered into a setup mode and the CMOS information is to be saved, it is saved to both the CMOS memory and to the serial EEPROM. Upon booting up, a check is made to see if the CMOS memory has not lost data. If it has, then the copy stored in the serial EEPROM is retrieved and utilized. In a second embodiment, a flash EEPROM used to store the BIOS of the computer also stores this information. The flash EEPROM is a type where the EEPROM is divided into several partitions and each can be programmed independently of the others. The partition of the flash EEPROM used for the CMOS information is originally erased. The partition is sufficiently large to contain numerous copies of the CMOS data. Copies of the CMOS data are sequentially stored. If the partition should become filled up, then an erase cycle is performed and the CMOS data is written as the first copy. If upon booting the computer indicates that the CMOS memory is not trustworthy, then the partition is scanned until erased state of data is obtained, at which time the pointer is decremented to obtain the last copy of the stored CMOS data and this is restored for operation.