BIOS & CMOS

• BIOS is an abbreviation for Basic Input/Output Services
• CMOS (pronounced “see-moss”) is an abbreviation for Complementary Metal–Oxide–Semiconductor.

Introduction:

This is a topic that has waxed and waned in its importance over the years. It wasn’t that many years ago that as a technician you would receive special secret training on the computer’s BIOS by men in hooded robes. The A+ exam would ask several questions about the types of BIOS, the ways to edit the BIOS & CMOS, and to identify the chips on the motherboard. In today’s modern computers the BIOS and CMOS are still vital to the functioning of the computer but is much more hands off. As a technician you need to know BIOS/CMOS light, in other words, you do not need to know it in excruciating details.

The Big Picture

In the computer you have two families, the hardware (physical objects) and the software (made of bits and bytes), and they do not know how to talk to each other.

When programmers are creating their works of binary art they cannot write code for each possible hardware device in existence. We need something to communicate between the hardware and software. We need a middleman, a translator that can work with the software and hardware. The translator, the go between is the BIOS.

The BIOS is very rudimentary software that allows the software to work with the hardware without  ever having to actually talk to each other. It allows software to work with a myriad of hardware without ever having to deal with it directly. This middleman allows programmers to write software without even knowing, or caring how the hardware works.

LabRats: BIOS Basics

Troubleshooting

I have discussed this in other podcasts, but now would be a good time to refresh. When working on a computer they’re 5 places were a computer problem can occur. When trying to diagnose a computer you must determine what category the problem exists in.

Mr. Ford’s 5 categories of PC problems:

1. Hardware- it is a problem with a component of the computer
2. BIOS/Drivers- there is a problem with the software’s ability to communicate with the hardware
3. Operating Systems- there is a problem with Windows, Mac OS X, or Linux
4. Application- the program is going bad
5. User- the person working on the computer made a mistake

ROM

In the last post and podcast we looked at RAM. RAM and ROM are distance cousins. RAM is Random Access Memory, it is volatile, meaning when you turn the power out, the information is gone. ROM is Read Only Memory, and wow is the name misleading. ROM is Random Access Memory but it is non-volatile. When you turn the power off the information in the ROM remains, it is “constant as the northern star, Of whose true-fix’d and resting quality.”

RAM is volatile, ROM is non-volatile

BIOS is stored within the ROM. Every motherboard and many hardware components have ROM, with the BIOS held within.

Over there years there have been several types of ROM. The best part is they are no longer on the A+ exam. For those of you who are curious here is a short list

Disclaimer for the Computer Engineer Geeks-this is a short summary of some the types of ROM that have been in the market. This brief expiation works for the computer tech. So no hate mail.

• PROM
  • Programmable read-only memory
  • This type of ROM came from the factor with all the information already on the chip. It could not be changed
• EPROM
  • Erasable programmable read-only memory
  • This type of ROM could be changed by exposing it to strong UV rays
• EEPROM
  • Electrically erasable programmable read-only memory
  • Could change the ROM through electricity from the computer or other device
• Flash memory
  • Current type of ROM
  • Very similar to your flash drives

Flashing the BIOS

One of the advantages of today’s BIOS is they can be updated. In the old days if you could update your BIOS you would need special tools. In today’s PC anyone can update “flash” their BIOS.

Before we flash the BIOS the big question is, why would you want to? When motherboards are released to the consumer they are not always bug free, or maybe a new technology come out that was not originally supported. The reason to flash the BIOS is to increase functionality, it fixes problems. That does not mean that every person needs to flash their BIOS, but if there are strange hardware problems, and more importantly if the manufacture says there is a problem that needs to be fix, then flash the BIOS.

Today’s computers can be flashed through an online update, or a software program. On my MacBook Pro I recently had a firmware (BIOS) update done online. This one rule is true regardless of who you are, or the type of BIOS, when you start to flash your BIOS you must complete the job! You CANNOT stop the process while it is going on. Make sure you will not lose power (so no flashing in thunderstorms), and have the time to follow through. If you mess up the flashing you may have just turned your PC into an expensive paperweight.

LabRats: Flash Your BIOS

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CMOS

The BIOS supplies the basics method for hardware and software to communicate. The CMOS is the user interface area that allows you to make changes to how software and hardware interact.

In the CMOS you can change the boot order, CPU fan speed, passwords, USB support, SATA support and tons of other stuff.

The CMOS used to be held on a separate chip on the motherboard. On today’s computers the CMOS could be either within the BIOS chip or in the south bridge (more on the bridge in another posting).

Most average users will never mess with the CMOS, you however are not the average use, so lets get some CMOS under our fingernails.

Playing with CMOS

Most of the work you will need to do in CMOS is to change the boot order, which device the computer looks at first when it starts the operating system. To get into the CMOS you will need to press a specific key on the keyboard as the computer boots up.

When the computer is in the early, early process of starting, before Windows wakes up, keep and eye out for the “setup” option. The setup option is how you get into CMOS. Not all computers will display this option and when they do it usually is quickly displayed on the screen then disappears. Some of the typical buttons to hit are the DEL key, F2 key, or the F10 key. When in doubt you can always play the piano. A top-secret tip amongst techs is to spread you hands out wide, fingers open, and just starting hitting the keys (lightly, not pounding). More about booting into setup: http://miro.pair.com/How_to_Get_Into_The_BIOS.php

Now that you are in CMOS, be careful, you can really mess up your computer. I am not trying to scare you, just give you a healthy appreciation for the POWER of the CMOS.

Depending on who made your motherboard your CMOS could offer different options. There are a few standard options, most you will never and should never mess with in modern computers. For example in the old, old, old days you had to set the parameters of your hard drive. Today the hard drive and CMOS take care of it without your help. There are two or three menu option that you need to be aware of.

The first option is the boot order. The boot order allows you to pick which device you want to boot from. For example let say you need to reinstall the OS, but it will not boot from the CD or DVD player. Check this option and make sure the CD or DVD players are the first locations to boot from. Another helpful tech hint is to switch to hard drive as your first boot option to prevent people from booting to USB, floppies or CDs. This is important when you want to make sure people have a hard time bypassing security measure you may have place on your computer.

The second and third menu options deals with passwords. In the CMOS you can set password to do two things: 1) password to boot the computer, 2) password to modify the CMOS.

For the most part all the other options are either better left alone, or are explained in the motherboard’s manual.

For more on BIOS/CMOS setting check out my friends at PCMech: Configure the BIOS

CMOS Storage

BIOS is held on ROM. Currently the ROM is very much like the flash drives that you can use to hold your files. The CMOS is not held in ROM, it is held in volatile memory. When the power goes out, the contents of the CMOS get wiped. Because the CMOS can be erased without power, the geeks of old place a single watch batter on the motherboard to maintain the contents of the CMOS.

Test Tip: Back in the day the CMOS kept the time for the computer. If you are asked on the A+ exam: “The computer is losing time what is the most likely problem?” The answer is the CMOS batter is going bad. Having said that I have never had to replace the CMOS batter. Usually by the time the batter goes bad it is time for a new computer. Watch out, if the test asks, “The computer is exactly 1 hour slow, or 2 hour slow” the problem is the computer was never set up to the correct time zone. So when the computer is exactly XX hours fast or slow it is a time zone problem, when it is a general loss of time, look at the CMOS battery.

The nature of the CMOS allows us to recover from bad choices. If you have set something on CMOS that appeared to be a good idea at the time, but not so much now. You can always reset the CMOS to factory defaults. You can use the CMOS jumpers on the motherboard, or you can always just take the battery for a few seconds.

Stumble it!