CMOS and BIOS

[lunatic]

Had a conversation earlier today and realized that I had not the slightest clue as to what CMOS was. Call me stupid, but everyone has to learn these things sometime =). So anyway, I asked someone that I thought would know, and the person replied that CMOS and BIOS were similar/the same thing. I just wanted to know the differences/similarities bewteen the two for further reference.<p>As always, any help or replies would be appreciated. Sorry if my questions bother one of you, since they are probably fairly simple to answer to one who has a decent knowledge (perhaps).

[Chris Smith]

C = Complementary
M = Metal
O = Oxide
S = Switch<p>Often "mis" used as Bios

[bobsRAC]

CMOS refers to a semiconductor device utilizing Metal Oxide Semiconductor Field Effect Transistors (MOSFET). Older chips used Bipolar Junction Transistors (BJT) and were known as TTL.<p>BIOS refers to a computer's Basic Input Output System (BIOS). The BIOS is a set of low-lovel instructions the computer used to boot and to control some on-board hardware. The BIOS is often implemented in Erasable Programmable Read Only Memeory (EPROM).

[bobsRAC]

TTL by the way is Transistor-Transistor-Logic.

[ampedtech]

bobsRAC is right on!<p>check out NUTS and Volts on line Encyclopedia<p>http://www.nutsvolts.com/Encyclopedia.htm<p>you might look at cmos or TTL as a discription of the eletrical characteristics of a manufacture process.<p>voltage levels, current consumption, fan out (how many like inputs can be suppled by an output)<p>The reason cmos and bios have been used to describe one another is that cmos uses a SMALL amount of current. This makes cmos a good choice
for storing somewhat variable information that your computer needs to startup(boot). Stuff like:<p>How much memory do I (your computer) have?<p>What kind of harddrive do I have?<p>What time is it? (the real time clock runs in cmos)
Which hard drive or floppy to boot to.<p>Look at your setup (before windows starts) most of the parameters in setup are stored in the cmos portion of your bios.<p>When your computer has been unpluged for a long time it still "remembers" this stuff.<p>The internal battery is used to send tiny current pulses to refresh your cmos or bios memory.<p>Not all bios is stored in cmos. Some bios data is stored in ROM.