What is CMOS?

Alternatively known as an RTC (real-time clock), NVRAM (non-volatile RAM), or CMOS RAM, CMOS is short for complementary metal-oxide semiconductor. CMOS is an onboard, battery-powered semiconductor chip inside computers that stores information. 

This information ranges from the system time and date to your computer's hardware settings. The picture shows an example of the most common CMOS coin cell battery (Panasonic CR 2032 3V) used to power the CMOS memory.

History of CMOS-

The Motorola 146818 chip was the first RTC and CMOS RAM chip to be used in early IBM computers, capable of storing 64 bytes of data. Since the system clock used 14 bytes of RAM, this left an additional 50 bytes for storing system settings. Today, most computers have moved the settings from CMOS and integrated them into the southbridge or Super I/O chips.

How long does the CMOS battery last?

The standard lifetime of a CMOS battery is around 10 Years. However, this can vary depending on the use and environment where the computer resides.

Which devices use CMOS?

• Digital logic circuits
• SRAM (Static RAM)
• Microprocessors
• Microcontrollers

How would I know if my CMOS battery is failing?

If the CMOS battery fails, the computer cannot maintain the correct time or date on the computer after it's turned off. For example, after turning your computer on, you may notice the time changed to 12:00 P.M., and the date is reset to January 1, 1990. This error indicates the CMOS battery has failed.

Another indication of CMOS battery failure is if one of the following messages are shown as the computer boots.

• CMOS Read Error
• CMOS Checksum Error
• CMOS Battery Failure
• System battery voltage is low

Apple computer users-

PRAM is the Apple Macintosh equivalent of CMOS.

How do you pronounce CMOS?

CMOS is pronounced as one word that sounds like see-moss.

What is SATA?

Short for serial AT attachment, SATA 1.0 was first released in August 2001 and is a replacement for the parallel ATA interface used in IBM compatible computers. SerialATA can deliver 1.5 Gbps (approximately 187 MBps) of performance to each drive within a disk array. 

It is backward-compatible with ATA and ATAPI devices, and offers a thin, small cable solution, as seen in the "SATA Data Cable" picture. This cable helps makes cable routing easier and offers better airflow in the computer compared to the earlier ribbon cables used with ATA drives.

SATA also supports external drives through External SATA more commonly known as eSATA. eSATA offers many more advantages compared to other solutions. 

For example, it is hot-swappable, supports faster transfer speeds with no bottleneck issues like USB and FireWire, and supports disk drive technologies (e.g., S.M.A.R.T.).

However, eSATA does have some disadvantages, such as not distributing power through the cable like USB, which means drives require an external power source. 

The eSATA cable also supports a maximum length of up to 2 meters. Because of these disadvantages don't plan on eSATA becoming the only external solution for computers.

What hardware uses the SATA cable?

The SATA cable is often used with hard drives but is also used with drives, such as disc drives.

How many pins does SATA have?

There are two types of SATA cables. The SATA data cable that transmits the data between the drive and the motherboard has seven pins. The SATA power cable that connects to the power supply has fifteen pins.

Where is the SATA connector on the motherboard?

The location of the SATA connector on a motherboard varies by motherboard manufacturer. Often these connectors are found on one of the edges of the motherboard for easy access. See the picture of a motherboard for an example of a motherboard with SATA connectors on the left side of the motherboard.

How do you pronounce SATA?

SATA should always be pronounced as a full word or partial full word and never as each letter sounded out. 

However, its exact pronunciation is disputed. Many pronounce it sah-tuh and others pronounce it say-tuh. It is also not uncommon to hear it pronounced as serial ay tee ay.

Because there has never been an official mention of how SATA is pronounced, we suggest using whichever full word or partial full word version sounds best to you.