The basic input-output system includes a software code that provided a computer with basic instruction so that it can start. When a computer turns on, it runs the program within BIOS to do some basic system checks, locate the operating system on a disk, and start.
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| basic input-output system |
The program within BIOS is store in a chip on the computer that rewritten. The older computer used an electrically is an erasable programmable read-only memory chip (EEPROM) for the BIOS. Read-only memory (ROM) has gone through several interactions over the years, from programmable read-only memory (PROM) to erasable programmable read-only memory (EPROM), an EEPROM. the new computer uses a for the type of flash memory, similar to what is uses with USB thumb drives.
The BIOS is often referal to as firmware. It is a hardware chip that can be physically seen and touched, and it includes software that runs code on the computer. the combination of hardware and software is the firmware.
BIOS VS. C MOS
The term complementary metal-oxide-semiconductor (CMOS) in the study of the computer the difference between BIOS and CMOS needs to be understood.
BIOS:-
This is the firmware. it stores the instruction for starting the computer and includes a program that to change some settings. the firmware can be updated in a procedure as flashing the BIOS.
CMOS:-
This holds only the user-configurable BIOS settings, such as the current time. Users can change these settings by asserting the BIOS applications. CMOS is volatile meaning the data is lost if the system turns off. the motherboard includes a CMOS battery to retain the CMOS data the system turns off. BIOS is the applications while CMOS is the data, and a CMOS battery keeps the CMOS power to retain the settings. Unfortunately, it's misleading.
Technically, CMOS is a specific type of chips that found on any motherboard, to store the user-configurable settings instead of CMOS, the data store on battery power static RAM. Sometimes, it is store in the same as a real-time clock that is keeping time. just like CMOS, these chips are power by a battery when the system turns off to ensure the system keeps these settings.
when the BIOS is using newer flash memory, the user-configurable data is often Store on the same chip as the BIOS application. due to how much memory store data doesn't even need a battery.
The real-time clock still needs a battery to keep time when the system turns off. even though the system no longer has CMOS, and this battery isn’t powering the CMOS, it is commonly the CMOS battery. even the CompTIA objective refers specifically to CMOS and the CMOS battery.
BIOS Components Information
The BIOS to verify the different components that install on a system. this can be useful to ensure that the system is recognizing newly install hardware. for example, if a new RAM installs but not recognizing, the BIOS can sometimes give insight into the problems.
The figure shows a screen from a different BIOS version with the system information page selected.
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| BIOS Configuration |
This page shows information about the processor type, processor cache, and memory. the processor is an Intel Core i7, with a 133-MHZ clock multiply by 20, giving a CPU speed of 2.66 GHz. the system has 12 GB (12,288 MB) of RAM install. The RAM speed of 1,066 MHZ (using a 133-MHZ clock multiply by 8) and is DDR3 SDRAM.
Additionally, most systems will automatically detect the presence of different drives and report their presence within BIOS. This includes hard disk drives and different types of optical drives, such as DVD drives. Sometimes, these settings are reported in the standard CMOS of features page, it is existing, and other times the settings are on a dedicated page for the drives.
drives might report as SATA1, SATA2, and so on if the system is using the SATA interface. if the system is using an EIDE interface, they might report as IDE, EIDE, or as hard disk drives this can be useful if a new drive has been install but is not recognizing after starting.
Then, one has to go into BIOS, find the drive settings, and ensure that the new drives in recognized by BIOS. if it's not recognized, the hardware such as the cable is the configuration that has to be checked.
BIOS Configuration
There are a few configuration settings that are important to understand. Changes that made in the configuration remain in the system even after the system power off.Time and Date:
A very basic setting for the BIOS is the time and date. these settings saw on the very first page on the BIOS, which is sometimes the main page on the standard CMOS features page. the computer keeps time with a real-time clock, and the CMOS battery keeps the clock ticking even when the system is turned off.
This rarely nice to be changed except when the CMOS battery is failing. if the battery is failing, the real-time clock because slow and needs to be reset often.
when replacing the battery make sure that it replaces with the correct type. motherboard manufacture warns the users that the wrong battery could explode. Also, local regulations should we followed when disposing of the original battery.
Boot Sequence:
One of the most important BIOS settings for a technician to understand is the boot sequence. the boot sequence settings tell the computer about the device from which it should try to boot first.
if the hard drive does not have a bootable operating system, it will look for a bootable operating system on the CDROM, then on a floppy drive, and then by using PXE.
As configures, it will never boot using the CD ROM drive, unless the hard drive fails if the booking has done using a bootable CD ROM drive, the configuration to change.
Clock Speed:
The motherboard typically includes serial present detect (SPD) cheap that detects and stores the speed of the CPU and the RAM. the BIOS either reads the data from the SPD chip or automatically detects the clock speeds and reports them.
Some BIOS utilities allow manipulating these clock speeds by altering the frequency, the multiplier, or the voltage.
For example, if a system has a 133-MHZ clock and a 20x multiplier, the speed is 2.66 GHz. is if the clock changes from 133 MHz to 148 MHz, the speed is 2.26 GHz. if the multiplier changes from 20x to 24x, the speed is 3.55 GHz.
Security:
Many BIOS utilities include security settings, and the most common security setting is related to BIOS passwords. other possible settings are related to a Trusted Platform Module (TPM) and LoJack.
looking again at the given figure, the settings for a supervisor password, and user password seen.
when setting the supervisor password provide full control over any BIOS settings and it sometimes set by an administrator to ensure that they can override any changes made by a user.
depending on the BIOS, the user password provides varied access it might allow the user to do anything except change the supervisor password, or it might allow the user to change only limited setting such as the date and time. in some systems, it requires a user to enter the password every time the system started.
POST and Other Diagnostics:
POST is an in-built diagnostic tool that starts the processor of a computer starts. verifies that the various hardware components of a computer such as a keyboard, random access memory, and disk drive are functioning properly.
if POST is successful that then the computer begins to boot, else the BIOS issue an error message. the error message is in the form of serial of Beeps these beeps may have a pattern of long beeps or short beeps or a combination of the two depending on the nature of the problem.
The patterns of beeps convey information about the type of fault detected. for example, if the is unable to detect the processor if we stop the boot process and convey the message through a code of beeps.
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