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CMOS BIOS in simple terms

By gbrownlee ·
As I understand it, a bios is neither software or hardware, but I thought this section to be the best to get a reply.

From circa Windows 95 to the present day, has the relationship between the two changed? Why is/was it bad news if you lost your cmos settings. Can't you just enter the bios and use defaults. Do the cmos batterys in newer motherboards recieve a trickle charge when the pc is in use and changing the cmos every 2 years be a non issue now. Why are there such dire warnings about entering the bios and making changes. What kind of changes would make the system un-bootable, if any.

I read, in a city newspaper an advertisement for instant on pc's. Does this mean a change in which the bios functions, and what has happened to the POST?


ps. answers to this question WILL BE RATED!!

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by TheChas In reply to CMOS BIOS in simple term ...

BIOS stands for Basic Input Output System.

The system BIOS IS software.
This software is stored in a special type of memory called Flash ROM.
The advantage of flash ROM is that the software code stored in the ROM can be changed. (BIOS update)

The CMOS RAM on a PC is used to store the customization settings that configure the BIOS to properly function with your hardware.

CMOS stands for Complementary Metal Oxide Semi-conductor.
CMOS is the "technology" of the RAM chip that stores the BIOS settings.
The advantage of CMOS technology is that it requires very little power to save the settings, and can be easily powered for years by a battery.

For most PCs, it will result in less than optimum performance if you simply use the BIOS default settings.
The CPU, memory, and drives may not transfer data as fast as they are capable.
The USB ports may not be enabled.
The printer port is usually not set to the ECP/EPP mode required by scanners and many printers.
The POST part of the boot process can also take longer using default settings. As time will be spent looking for drives that do not exist.

Nearly all "modern" motherboards use Lithium coin cell batteries. These are NOT rechargeable.

However, for nearly all ATX style motherboards, the computer is never completely off.

As long as power is applied to the power supply, a low current 5 volt supply is always present on the motherboard.
This low current supply provides power for the power control circuit, the real time clock, and the CMOS RAM.
So, the battery only is used when power is turned off. Like in a power outage. Or if you use a power strip and switch it off after the computer shuts down.

Yes, there are settings in BIOS setup that can cause the PC to not boot, and could cause data loose on the hard drive.


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by TheChas In reply to

On the newest systems that use AMD socket A, or Intel Pentium 4 processors, there are settings that could burn up the CPU.

Things like:
CPU Core voltage.
CPU speed.
RAM speed and timing settings.
Hard drive parameters.
Power management options.
Can all be set in ways that could cause a system to not boot, or even cause some damage.

As to instant on PCs, there are 2 ways to handle this:

1. The PC never fully shuts down and sits in a standby mode when it appears to be off.

2. Fixed hardware configuration. If you build the PC with a specific set of hardware, and do not allow for the hardware to be changed, you can use a smaller BIOS program with all of the settings pre-set.
That way, when you power on the PC it does not need to verify what hardware is present. Therefore, it can skip the POST tests and go straight to loading the operating system.

Hope this helps.


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by gbrownlee In reply to

Poster rated this answer.
A very clear and concise answer. My apologies for the measly points award, but I blew just about half of my tech points on my first question posted at TR.

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by CG IT In reply to CMOS BIOS in simple term ...

you ought to give Chas more points than 300 for this acurate, highly definitive explanation of CMOS and BIOS.

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by gbrownlee In reply to

Poster rated this answer.
I think Chas's answer deserves more too. If you could see your way clear as too lending me, say.....10,000 points, I will gladly spread them around! As for now, I have to save some incase an "emergency " situation occurs.

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by sgt_shultz In reply to CMOS BIOS in simple term ...
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by gbrownlee In reply to

Poster rated this answer.
Hey Sarge...If you want, I'll lay down and then you can kick me while I'm down; on tech points that is. When you are relatively new to the IT world and TR, it is really tough trying to get the amount of points necessary to be able to spend freely.

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by gbrownlee In reply to CMOS BIOS in simple term ...

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