BIOS versus CMOS
 

I'm a new tech and I'm studying for the A+ exam. And I need some help understanding the differences between the BIOS and CMOS. It seems like they are the same thing or at least very similar but it seems as though they are completely different when it comes to sample test questions.

Thank you for any help.

The BIOS is computer code. It is comprised of hardware drivers.

The CMOS is non-volatile RAM used to store the BIOS, some bootstrap code, and some information about the hardware in the machine.

Modern operating system have their own hardware drivers so the BIOS is generally just used to boot the operating system.

BIOS stands for Basic Input Output System, it is code, stored in hardware. It tests and inializes your hadware when power is first applied.

CMOS is a type of storage, hardware only. You can store the BIOS code in CMOS.

Hope this helps.

One more question, hopefully :D

IDE versus ATA. I know both terms are used to describe ATA drives. But I just read that IDE is technically incorrect to describe an ATA drive. So what is exactly is IDE? Is it simply the elimination of controller cable because the disk controller in integrated into the hard drive?

Also are SATA drives also referred to as IDE drives?

Okay. I got this from a quick ask.com search.

Fragments from
http://www.promethos.org/lxr/http/so...rs/ide/Kconfig
The following is from my memory banks.

The disk specification that we think of as the common PC hard disk was originally called a Winchester disk. This specification was developed jointly by IBM and Seagate.

In the beginning there was the MFM disk controller. I don't recall what MFM means.

Then the was the RLL disk controller. RLL stands for Run Length Limited. It refers to the method of writing data to the disk platters.

Of course you don't see MFM or RLL disks any longer. I just included these for completeness. IDE replaced MFM and RLL controllers.

They are not the same thing and they're not even similar. It's apples and applecart building materials.

BIOS - Basic input/output system is embedded code that controls hardware on computer systems.
CMOS - Complementary metal-oxide semiconductor- is a physical and chemical description for a class of solid state devices characterized by low power consumption. Devices built from CMOS components trade off speed for low power consumption and reduced environmentals. In the old days (and maybe even today) they built computers from ECL on GaAs substrates. They were fast but had to be water cooled. Later they went to TTL but they still consumed a lot of power and needed tightly regulated high-quality power supplies. CMOS is slower than those technologies but it runs in a wide range of supply voltages and doesn't need to be water cooled so it's a lot cheaper. And water cooled laptops just never caught on :p

CMOS is not just storage- it's the name for the technology that devices are built on. They can certainly be storage but they can also be logic devices, CPUs, switches, busses, MUXes/DEMUXes etc.

You forget to say that the reason they called it the Winchester disk was that after a head crash you took out the platters, tossed 'em up in the sky, and yelled "pull!" :p