The CMOS Battery

The CMOS Battery

The CMOS chip requires a small trickle voltage from a battery to keep its memory alive. When the battery gets low or runs out of current, the computer will experience a sudden memory loss and thus lose settings. The voltage of CMOS batteries ranges from 3 to 6 volts. These Batteries come as either on-board (NiCad batteries, soldered in place or in a fixture, that last from five to seven years) or external (No rechargeable AA alkaline batteries that last from two to four years).

Some time to load the default setting of the CMOS setup; remove the CMOS Battery for few mints and place it again on the motherboard. The first clue that the battery is weakening is that the CMOS clock begins to slow down. Go to a “C” Prompt and type time. If you notice the clock is slow, it's time to change the battery.

A Typical CMOS Setup

A Typical CMOS Setup

CMOS stands for Complementary Metal Oxide Semiconductor. All PC,s have CMOS chip. In CMOS chip the basic information about computer are recorded permanently, such as date and time, number of installed Floppy Disk, Hard Disk, there configuration, and password etc. The CMOS setup programs are text-based. CMOS setting (such as booting sequence, Date, Time, so on) can be change by using keystrokes to navigate through the information. The Function of CMOS is same as RAM, but to maintain permanent information in CMOS chip a small battery is attached to CMOS chip called CMOS battery.

ROM BIOS

ROM BIOS

ROM BIOS stands for Read Only Memory; Basic Input/Out put System. ROM is a type of memory that stores data even when the main computer supply is turned off. So, the information that initially required to turn On or run the computer are stored on the ROM. The BIOS, software in the form of programs stored on ROM chips, is used during the startup (Boot up) routine to check out the system and prepared to run the hardware.

More recent systems use a technology called flash ROM or flash BIOS that allows code in the core chips to be updated by software available through the BIOS or motherboard supplier. BIOS (also called firmware) can be subdivided into three classes, depending upon the type of hardware it controls.

ROM Chips

·        Mask ROM

·        PROM

·        EPROM

·        EEPROM

·        Flash ROM