What It Is and What It is For

CMOS is the time period normally used to explain the small quantity of reminiscence on a pc motherboard that shops the BIOS settings. A few of these BIOS settings embody the system time and date, in addition to {hardware} settings.

Different Names for CMOS

CMOS (pronounced see-moss) is hardly each described by its full identify: complementary metal-oxide-semiconductor. Nonetheless, it’s typically known as Actual-Time Clock (RTC), CMOS RAM, Non-Risky RAM (NVRAM), Non-Risky BIOS reminiscenceor complementary-symmetry metal-oxide-semiconductor (COS-MOS).

Clearing CMOS

Most discuss of CMOS entails clearing CMOS, which implies to reset the BIOS settings to their default ranges. This can be a very easy activity that is an incredible troubleshooting step for a lot of sorts of pc issues.

For instance, possibly your pc is freezing up in the course of the POST, by which case clearing the CMOS to reset the BIOS settings to manufacturing facility default ranges, is perhaps the best resolution.

Or possibly you’ll want to clear CMOS to reset misconfigured BIOS settings to repair sure hardware-related error messages, comparable to Code 29 errors. Different CMOS errors revolve round low battery voltage, CMOS checksum, battery failure, and skim error.

How BIOS and CMOS Work Collectively

The BIOS is a pc chip on the motherboard like CMOS, besides that its function is to speak between the processor and different {hardware} parts just like the laborious drive, USB ports, sound card, video card, and extra. A pc with out a BIOS would not perceive how these items of the pc work collectively.

The BIOS firmware can be what performs the Energy On Self Take a look at to check these items of {hardware}, and what finally runs the bootloader to launch the working system.

CMOS can be a pc chip on the motherboard, or extra particularly a RAM chip, which implies it will usually lose the settings it is storing when the pc is shut down (identical to how the contents of RAM aren’t maintained every time you restart your pc). Nonetheless, the CMOS battery is used to offer fixed energy to the chip.

When the pc first boots up, BIOS pulls data from the CMOS chip to grasp the {hardware} settings, time, and anything that is saved in it. The chip sometimes shops as little as 256 bytes of data.

What Is a CMOS Battery?

The CMOS is normally powered by a coin-sized CR2032 cell battery, known as the CMOS battery.

Most CMOS batteries will final the lifetime of a motherboard, as much as 10 years most often, however will typically must be changed relying on how the gadget is getting used.

Incorrect or sluggish system date and time, and lack of BIOS settings, are main indicators of a useless or dying CMOS battery. One other indication of a useless CMOS battery may very well be a crimson mild on the motherboard.

Changing the CMOS battery is as simple as swapping out the useless one for a brand new one. You will get a brand new CMOS battery on Amazon and thru different retailers that promote pc alternative elements.

Extra About CMOS & CMOS Batteries

Whereas most motherboards have a spot for a CMOS battery, some smaller computer systems, like many tablets and laptops, have a small exterior compartment for the battery that connects to the motherboard by way of two small wires.

Some gadgets that use CMOS embody microprocessors, microcontrollers, and static RAM (SRAM).

It is vital to grasp that CMOS and BIOS usually are not interchangeable phrases for a similar factor. Whereas they work collectively for a selected operate inside the pc, they’re two fully totally different parts.

When the pc is first beginning up, there’s an choice to boot into BIOS or CMOS. Opening the CMOS setup is how one can change the settings it is storing, just like the date and time and the way the totally different pc parts are first began up. You too can use CMOS setup to disable/allow some {hardware} gadgets.

CMOS chips are fascinating for battery-powered gadgets like laptops as a result of they use much less energy than different sorts of chips. Though they use each damaging polarity circuits and constructive polarity circuits (NMOS and PMOS), just one circuit sort is powered on at a time.

The Mac equal to CMOS is PRAM, which stands for Parameter RAM. You too can reset your Mac’s PRAM.