CMOS setup or BIOS setup?
Posted 09 February 2012 - 09:42 PM
Posted 10 February 2012 - 09:54 AM
In computers, the "firmware" uses a special memory device (typically an EEPROM device) that is programmed semi-permanently (thus "firm") with the BIOS information. It is "firm" because this computer memory chip, once programmed, does not need any power (voltage) to retain (remember) its stored programming. This is where all the default BIOS information is stored ("flashed" or "burned") at the factory.
User customizations (date and time, drive information, boot order, and other changes you may make in the BIOS Setup Menu) are stored in the CMOS. A CMOS device is another special memory device that MUST HAVE power ("holding" voltage) applied to it at all times, or else it dumps it stored data. The transistors that previously held all the 1s and 0s that represented the stored data all "flop" back to their "quiescent" state of no data stored. When the saved data in the CMOS "chip" is dumped, the BIOS is "reset" - that is, taken back to the default settings. This is why you must have a good motherboard (CMOS) battery to maintain that "holding" voltage on the CMOS memory device.
So, to answer your question, it all depends on which device you are talking about. The firmware stores the BIOS, the CMOS stores changes to the BIOS. Together they form the basic set of instructions needed to boot the computer.
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