What is BIOS?
BIOS = Basic Input Output System
BIOS is identified as a group of programs, which are solidified to the ROM (read-only memory unit, which doesn’t allow for modifications) chip of a computer’s motherboard. BIOS is where the most basic yet important input and output programs of a computer, system settings, and self-triggered programs are saved. BIOS is firmware, which is used to perform hardware initialisation during the posting process, furthermore, it also provides runtime services for operating systems and programs.
(Firmware: Firmware is a specific class of computer software provides low level control for a devices specific hardware)
Any changes that a user is willing to do in the BIOS ecosystem must be executed carefully, as incorrectly inputting data into the BIOS could lead to the computer not booting at all.
The same applies to upgrades that a user wants to do on the BIOS. The user must make sure that the BIOS they are upgrading to, is compatible to the computer system which they have.
Otherwise, if the BIOS is not compatible, then this could potentially corrupt the BIOS system, which means that the computer wont be able to boot.
What does BIOS do?
BIOS is responsible to load the basic computer hardware and to initialise the booting of the operation system. Before the system boots up, BIOS will have to carry out tests to make sure that everything on the computer meet the requirements for the boot to initiate.
This test is referred to as “POST” (Power On Self Test). If the test fails, the computer will start beeping to indicate that the POST test had failed.
#1. Check CMOS Setup for settings
BIOS setup is a configuration program that permits us to configure hardware settings. This is known as CMOS (Complementary metal oxide semi-conductor).
The first thing that BIOS has to do is check the information in a small memory unit, which is referred to as “CMOS chip”.
CMOS Setup provides detailed information, which is specific to your system.
The setup includes many functions, some of which are mentioned below:
- Changing booting order
- Creating or deleting of BIOS password
- Changing CPU settings
- Changing Memory settings
- View CPU and system temperatures
- Changing and view fan speed settings
- Change system voltages
#2. Interrupt handlers and device drivers are loaded
A collection of programs that are stored in non-volatile memory chips, specifically either EEPROM (Electrically Erasable Programmable Read Only Memory) or EPROM (Erasable Programmable Read Only Memory), they are positioned on the motherboard. These drivers will give basic information about the computer hardware.
The interrupt handlers are small pieces of software, which act like translators between the operating system and the hardware.
For instance, if a key on the keyboard is pressed, a signal is sent to the keyboard interrupt handler, which will tell the CPU what this is and then pass it to the operating system.
Device drivers also identify other hardware components such as hard drive, mouse, and keyboard.
#3. Power management and registers are initialised
With the early computers, and old versions of Microsoft, when a computer is booted, you can see what the BIOS is doing. On many various machines, the BIOS will display a series of texts one after another portraying the concurrent executions of checks that are happening, i.e. the amount of memory installed on the computer system, or the type of hard disk etc.
The BIOS also determines whether the video card in the computer system is functional. Usually most video cards have a BIOS of their own that initialises the memory and graphics processor on the card. If the video cards do not have a BIOS, then there is usually video driver information on a ROM memory unit on the motherboard that the BIOS can load.
#4. Checks if the system requires a cold boot or a reboot
After that, the BIOS checks if the system requires a cold boot or a warm reboot. This is checked by checking the value of the memory address, if the value of 1234h comes out as a result, then that indicates a reboot and the BIOS skips POST. Anything else will be considered to be a cold boot.
|Cold boot/hard boot||Warm reboot/soft boot|
|System starts up from a complete powerless state||The system returns back to its original state without interrupting power|
|A cold reboot completely resets the hardware, it will clear the system of temporary memory||Keeps memory intact after a reboot, as it doesn’t reset components and the power source|
|A cold reboot can be done, when the system doesn’t respond to a warm reboot, or if the system was completely shut off||A warm reboot is executed when a program fails to respond, which will cause the system to freeze in between a session|
|Runs self diagnostics, which will reset hardware and memory||A full system diagnostic DOES NOT get executed, which allows reboot time to be reduced|
#5. Perform POST
If a cold boot is initiated, then the BIOS must make sure that the computer hardware is functioning as it should and that there are no issues with it. This is done by the “POST” (Power On Self Test) routine, which determines that the disk drivers, RAM, peripheral devices and other hardware components are properly working. Once the diagnostics show that the system are all in working order, the computer will boot, if they’re not in working order, and there is a fault the computer will generate beeping noises.
POST verifies the presence of required hardware components such as keyboard and determines the available amount of real memory.
Once the computer runs the POST routine, every adapter card in the system with a BIOS runs its own POST routine. Each manufacturer of the computer and adapter cards have a different visualisation of what the screen shows during POST processing.
Once everything completes its checks, they are compared with the configuration data in the BIOS, if any discrepancies arise, this will cause the POST routine to fail.
#6. System settings are displayed
During the POST process, BIOS will display some details about the system on the screen, this can be the processor, hard drive information, memory, and BIOS revision and date etc.
#7. Determine which devices are bootable
BIOS will look at the sequence of storage drives, which identify as boot devices in the CMOS setup.
BIOS will begin the boot sequence from the first device, and it will go through each device. If a device has a fault, or the files of the device cannot be found, then the booting sequence will come cease.
#8. Bootstrap sequence is initiated
Once the POST routine is complete, the BIOS will locate and identify the operating system. Once found, the BIOS will pass the control to the operating system.
Most common types of Errors that are associated with BIOS:
Failed to overclock
(Overclocking is the action of increasing a components clock rate, which means that it’s running at a higher speed than it was designed to run. Users can optimise components for gaming, although in most circumstances this is not recommended as you’re asking for more power than the component can handle i.e. the CPU/RAM)
This is when the BIOS settings have been cleared, the likely cause of this error could be from:
- CMOS battery failure
- The system having power issues
- Overclocking RAM or PCU
- Adding a new device to the hardware which is defective
This error typically happens when a new hard drive or usb drives etc. is connected to the PC.
Usually adding a new compatible device wouldn’t cause a problem, unless the component being added is failing itself.
CPU Fan Error
This error usually refers to the silent fans spinning slower than the normal fans in the CPU. This error can occur when the BIOS settings have been reset due to an improper shutdown or a power outage.
Boot Device Error
The boot device error is an error, which is most common with the new modern motherboards which accommodate for UEFI. This is because the new component such as a DVD drive or a hard drive could be set to boot up as a UEFI. Although UEFI is far more superior to the older MBR BIOS, this setting has been known to change when new devices are connected to the PC.
Is BIOS becoming outdated?
Current BIOS systems have been around for a long time, since around 1974, MS-DOS PC’s in the 1980s had BIOS.
Although BIOS has evolved and improved massively overtime, including extensions like ACPI (Advanced Configuration and Power Interface), which allowed BIOS to configure devices more easily as well as allowing it to perform advanced power management functions, like “sleep”.
However in comparison to modern day computers and technological advancements, BIOS hasn’t really advanced as much since the MS-DOS days.
The BIOS that is still being used today, has a serious limitation that can only boot from drives, which are 2.1TB, or less in size.
BIOS must operate in a 16 bit processor mode, and must have a 1MB of space to execute its processes.
Another limitation of BIOS includes that it has trouble initialising multiple hardware at once, which decreases efficiency, as it leads to a slow boot process.
Therefore BIOS has needed a replacement for long time, so in 2007 Intel, Microsoft, AMD, and PC manufacturers had agreed on “UEFI”, which is Unified Extensible Firmware Interface.
Nowadays the majority of computers use UEFI rather than BIOS.
With the new UEFI firmware, the limitation of hard drives being 2.1TB or less had been solved, and now UEFI can be booted on drives of 2.2 TB or larger, and as a matter of fact, the actual drive limit is said to be even 9.4 zettabytes (ZB), 1 ZB = 10007bytes
The reason for this, is because UEFI uses the “GPT” (GUID (Globally Unique Identifiers) Partition Table) partitioning scheme instead of “MBR” (Master Root Record), furthermore UEFI also boots the computer in a more standard way now, by launching EFI excitable programs rather than running code from the drive’s master boot record.
A partition structure will define how information is structured on that specific partition, it will also define if the code used in that partition is bootable.
MBR = Master Root Record
As MBR is getting dated with the new computer systems, it comes with its limitations such as that it only works on disks with a size of up to 2 TB in size and it can only support 4 partitions.
Despite those limitations, MBR is almost compatible with all devices (granted they are under 2TB in size)
GPT = GUID Partition Table
The advantage of using GPT is that it doesn’t have the same restriction of 2 TB disks, so it allows for nearly unlimited number of partitions.
An advantageous point of GPT is that it can store multiple copies of boot data across the disk, unlike MBR which only has it stored in one place. This feature of GPT is very beneficial as it makes it more robust and it can recover data if one of those copies gets corrupted.
Another advantageous point regarding GPT is that it stores “CRC” (cyclic redundancy check) values. This enabled GPT to notice if any of the data is corrupt, if so, it will attempt to recover the data from another disk location. In contrast MBR had no way of knowing if any part of the data was corrupt. All that will happen is, a system boot failure will appear on the screen, or even the drive partitions vanished, meaning a loss of data.
GPT also has a form of compatibility for old systems too, it does this by having protective MBR. This allows a single partition to extend across the entire drive. This allows the old system tools to not mistake the GPT drive for an unpartitioned drive, which means the GPT won’t be overwritten, which removes any chances of data loss.
Summary and Facts
BIOS = Basic Input Output System
BIOS is identified as a group of programs which are solidified to the ROM (read only memory unit, which doesn’t allow for modifications) chip of a computers motherboard. BIOS is where the most basic yet important input and output programs of a computers system settings, and self triggered programs are saved. BIOS is the software used when the computer software is booted, it does this by loading the aerating system in the computers memory.
BIOS is ultimately becoming outdated, there hasn’t really been a big significant change to BIOS since the 1980s, in contrast with the technological advances in computer systems.
Though in 2007, “UEFI” (Unified Extensible Firmware Interface) was developed, and now the majority of computer systems utilise it over BIOS.
One of the biggest advantages of using UEFI is that the hard drives don’t need to worry about being 2.1TB or less like with BIOS, this thanks to GPT (GUID (Globally Unique Identifiers) Partition Table). Other advantages due to GPT include, the storage of multiple copies of boot data across the system disk, which increases robustness as it can recover data if one of those copies get corrupted. In contrast, the traditional BIOS, which used MBR (Master Root Record), only had a single copy of the boot data, which means it is/was susceptible to boot data loss in case of corruption.
GPT also has a form of compatibility for old systems too, it does this by having protective MBR. This allows a single partition to extend across the entire drive, which allows the old system tools to not mistake the GPT drive for an unpartitioned drive, therefore meaning that the GPT won’t be overwritten.
What BIOS does
The functions of BIOS are a set of instructions, which are essential and fundamental part of a firmware on the systems motherboard. BIOS is responsible for checking that the hardware which is connected to the computer system is working fine before the system boots up. Once BIOS has done its checks, it hands over the control to the operating system.
Functions are which BIOS does
- Check CMOS Setup for settings
- Interrupt handlers and device drivers are loaded
- Power management and registers are initialised
- Checks if the system requires a cold boot or a reboot
- Perform POST
- System settings are displayed
- Determine which devices are bootable
- Bootstrap sequence is initiated
Most common types of Errors that are associated with BIOS
- Failed to overclock
- Failed Device
- CPU Fan Error
- Boot Device Error
Changing the settings of BIOS and upgrading it
One thing to keep in mind is that, a user must be very careful if they’re think about making any changes to the setup. Incorrect settings in the BIOS could lead the computer to not boot at all.
Users must be very careful when upgrading BIOS, as they must make sure that the BIOS that they’re upgrading too, is compatible to the computer system which they have. Otherwise, if the BIOS is not compatible, then this could potentially corrupt the BIOS system, which means that the computer wont be able to boot.