A power-on self-test POST is a process performed by firmware or software routines immediately after a computer or other digital electronic device is powered on. This article mainly deals with POSTs on personal computers, but many other embedded systems such as those in major appliances, avionicscommunications, or medical equipment also have self-test routines which are automatically invoked at power-on. The results of the POST may be displayed on a panel that is part of the device, output to an external device, or stored for future retrieval by a diagnostic tool.
Since a self-test might detect that the system's usual human-readable display is non-functional, an indicator lamp or a speaker may be provided to show error codes as a sequence of flashes or beeps. In addition to running tests, the POST process may also set the initial state of the device from firmware.
In the case of a computer, the POST routines are part of a device's pre-boot sequence ; if they complete successfully, the bootstrap loader code is invoked to load an operating system. In early BIOSes, POST did not organize or select boot devices, it simply identified floppy or hard disks, which the system would try to boot in that order, always.
The first memory location the CPU tries to execute is known as the reset vector. In the case of a hard rebootthe northbridge will direct this code fetch request to the BIOS located on the system flash memory. For a cold boot, for example, it may need to execute all of its functionality.
If, however, the system supports power saving or quick boot methods, the BIOS may be able to circumvent the standard POST device discovery, and simply program the devices from a preloaded system device table. The POST flow for the PC has developed from a very simple, straightforward process to one that is complex and convoluted.
During the POST, the BIOS must integrate a plethora of competing, evolving, and even mutually exclusive standards and initiatives for the matrix of hardware and OSes the PC is expected to support, although at most only simple memory tests and the setup screen are displayed.
This design by IBM was modeled after their larger e. As the PC platform evolved into more of a commodity consumer device, the mainframe- and minicomputer-inspired high-reliability features such as parity memory and the thorough memory test in every POST were dropped from most models. The exponential growth of PC memory sizes, driven by the equally exponential drop in memory prices, was also a factor in this, as the duration of a memory test using a given CPU is directly proportional to the memory size.
With people being more concerned with boot times now than in the s, the 30 to 60 second memory test adds undesirable delay for a benefit of confidence that is not perceived to be worth that cost by most users. This allows the user to set various options particular to the mother board before the operating system is loaded. If no key is pressed, the POST will proceed on to the boot sequence required to load the installed operating system. Both progress indication and error codes were generated; in the case of a failure which did not generate a code, the code of the last successful operation was available to aid in diagnosing the problem.
Once an operating system is running on the computer the code displayed by such a board may become meaningless, since some OSes, e. The actual numeric codes for the possible stages and error conditions differ from one BIOS supplier to another. Codes for different BIOS versions from a single supplier may also vary, although many codes remain unchanged in different versions.
Later BIOSes used a sequence of beeps from the motherboard-attached PC speaker if present and working to signal error codes. POST beep codes vary from manufacturer to manufacturer. Information on numeric and beep codes is available from manufacturers of BIOSes and motherboards. There are websites which collect codes for many BIOSes. In the event of a fatal error, the Mac will not make its startup chime.
Macs made after but prior toupon failing the POST, will immediately halt with a " death chime ", which is a sound that varies by model; it can be a beep, a car crash sound, the sound of shattering glass, a short musical tone, or more. On the screen, if working, will be the Sad Mac icon, along with two hexadecimal strings, which can be used to identify the problem. Macs made prior to crashed silently with the hexadecimal string and a Sad Mac icon.
When Apple introduced the iMac init was a radical departure from other Macs of the time. The beep codes were revised in October With the introduction of Intel-based Macs with EFI -based firmware, the startup tones were changed again. Amiga historical line of computers, from A to present an interesting POST sequence that prompts the user with a sequence of flashing screens of different colors rather than audible beeps as in other systems to show if various hardware POST tests were correct or else if they failed:.Also, learn how our PC starts.
To enable our CPU to communicate with other devices on our motherboard, we implement a special chip on the motherboard called a ROM chip. ROM chips that are installed on the motherboard contain programs that were burned into that ROM, that allow the CPU to communicate the with various devices attached to the motherboard. These devices include the keyboard, disk drives, memory, etc.
We should check for BIOS updates from manufacturers frequently. Devices that are connected to or are part of the motherboard can be categorized into three different categories. We have devices that have configurable parameters or that are likely to be changed from time to time.
How to Enter BIOS
And we have custom devices that may or may not be present in any given system. Devices that have no configurable parameters can be handled by the BIOS alone. Keyboard is an example of such device. For example, we may have 4 gigabytes of RAM on one machine, and 16 gigabytes on another machine.
The same thing is with disk drives.
We may have a hard drive installed in the system that has 40 gigabytes, and we could also have a 2 terabyte drive. When we add a new hard drive into the system, it will probably have different parameters than the one that was in our PC before. The CMOS also is where our system clock runs. Our operating system pulls time from the CMOS. If we shut the system off and turn it back on, the content of the BIOS is intact.
To do that, we have to use a battery. This battery keeps the contents of the CMOS chip intact while the system is shut down. The CMOS battery can be a low-voltage dry cell, lithium mounted on the motherboard, or even AA batteries in a housing clipped on a wall inside of the case.
The electric current is about 1 millionth of an amp and can provide effective power for years. Most systems use some kind of on board battery, shown on picture below.Access the BIOS setup utility to manage memory settings, configure a new hard drivechange the boot orderreset the BIOS password, and similar operations. Follow the easy steps below to access the BIOS setup utility on your computer, no matter what's on it— Windows 7Windows 10or Linux.
Restart your computeror turn it on if it's already off. Watch for an "entering setup" message in the first few seconds after turning on your computer.
This message varies greatly from computer to computer and also includes the key or keys you need to press to enter BIOS. Don't hold the key down or press it too many times or your system may error or lock up.
Как выполнить сброс BIOS или памяти CMOS и очистить память NVRAM на компьютере Dell
If that happens, just restart and try again. If you don't catch the key sequence needed to get into BIOS, reference one of these lists or check out the tips below:. Entering BIOS can be tricky, so here's some more help based on some common scenarios that I've seen:. Your computer may be configured to show your computer's logo instead of important BIOS messages.
Press Esc or Tab while the logo is showing to remove it. Some computers start too quickly to see the BIOS access message. Press any key to "unpause" your computer and continue booting. If you're having problems pressing that pause button in time, turn on your computer with your keyboard unplugged. You should receive a keyboard error which will pause the startup process long enough for you to see the keys necessary to enter BIOS!
Tweet Share Email. Here are some common ways you might see this BIOS access message:. Quickly press the key or keys instructed by the previous message. Use the BIOS setup utility as required. See a Picture Instead of a Message?
Having Troubles Pausing the Startup Screen? More from Lifewire.This is because they are very closely related to each other. In actuality, these two are nothing alike. BIOS is a type of software that manages the computer hardware when a computer boots-up. It is more like a primitive operating system that initializes all the resources needed by the true operating system.
On the other hand, CMOS is a type of integrated circuit.
These are the settings you change by accessing a menu during boot-up; commonly by pressing F2. One of the main reasons why CMOS was chosen is because of its very low energy consumption. The CMOS chip is constantly powered and when the system is off, a CR battery takes over the job to keep the information stored within. Once power is lost, the settings are also lost. It also runs for only a short period of time before handing control over to the true operating system.
While the contents of CMOS are important, losing it is not really disastrous for the entire system. It can easily be restored by going to the menu during boot-up. The BIOS code is very important as without it, the computer would not be able to boot.
To repair, the chip containing the BIOS needs to be removed and reprogrammed. There are many safeguards to prevent the corruption of the BIOS; including multiple restrictions to prevent accidental corruption and employing multiple chips containing the same BIOS for disaster recovery.
Flash memory has become the medium of choice for storage. Cite Ben Joan. February 20, Leave a Response Cancel Reply Name required. Email required. Please note: comment moderation is enabled and may delay your comment. There is no need to resubmit your comment.You can access BIOS configuration screens from the following interfaces:. Highlight the field to be modified using the arrow and Tab keys.
Use the left and right arrow keys to move sequentially back and forth through the menu screens.
Fields that can be reconfigured are displayed in color. All other fields are nonconfigurable. Modify the Setup field and close the screen. If you need to modify other setup parameters, use the arrow and Tab keys to navigate to the desired screen and menu item, and then repeat Step 1 through Step 4.
Otherwise, go to Step 6. Press and release the right arrow key until the Exit menu screen appears. Follow the instructions on the Exit menu screen to save your changes and exit the Setup utility.
How to Clear CMOS to Reset BIOS Settings in Systems with Intel® Desktop Boxed Processors
This section contains information and considerations regarding the system BIOS. Solaris Red Hat Linux. SUSE Linux. Windows The order in which the BIOS detects the Ethernet ports during bootup, and the corresponding drivers that control those ports are listed below:. General product information, including BIOS type, processor, memory, and time and date. Configure the boot device priority hard drives and the optical media drive.
Server devices can be configured by the BIOS if applicable. Set or change the user and supervisor passwords.If we can't tunnel through the Earth, how do we know what's at its center?
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Hottest Questions. Previously Viewed. Unanswered Questions. Computer Hardware. Wiki User Asked in The Difference Between What is the difference between startup bios and system bios?
Asked in Graduate Degrees What is difference between graduate and post graduate? The BIOS on a motherboard of a computer is an example of firmware. Tarancor maar foon ami khai moshla dya. A ROM is a copy of a game downloadable online. A BIOS is a file used to make an emulator work properly. Different BIOS developers may have differing distinctions on what each type of user can do. In general, an administrator can change settings in the BIOS, and a regular user cannot. Asked in The Difference Between Difference between pre-tensioned and post-tensioned?
The version of the Bios will usually post as a message during boot up. You can find your bios version there. The difference between modernism and post modernism are the highlights and approaches towards life.
It also differs in the ways of thinking that led to these movements. Search the web site of the motherboard or BIOS manufacturer to know how to interpred a series of beep codes. Most modern operating systems do not rely solely on the BIOS to support devices because interacting with them directly is usually faster, and bugs in the bIOS can be worked around. Asked in Computer Terminology What is the difference between a system password and a software password?
System password: PC bios password. Software password: Normal Software password. Asked in The Difference Between What is the difference between a thread and post? In computing terms - A 'thread' is a topic of discussion, and a 'post' is a response to the 'thread'.Post a Comment. Actually, they are different two things which are related with each other.
So its main function is save data. BIOS Setup program is stored in it, which saves important system information and system parameter. The most important input and output program of microcomputer, system information setup, POST and bootstrap program are saved there. When computer is starting, motherboard will take a series check and test on systems and peripheral devices. If you set it Enabled, computer startup speed will improve.
Boot Up Floppy - Seek. Boot Up NumLock — Status. Generally, the small keyboard in the right side of big keyboard is used as number keys default. If it is necessary, you can set it OFF, and small keyboard would become direction keys. Security Option. And only supervisor password could change parameters for CMOS. Follow the below:. And please remember back to main interface and press F10 and Enter to save these changes.
BIOS main function. It is a programmable interface between software and hardware in microcomputer system. It makes application software functions appropriate link up to microcomputer hardware. Just press boot key when you start computer and you will enter this program. When microcomputer is connected with power, POST will check equipment inside system. Once there is problem in check process, system prompt message will pops up for computer user.
Read operational system boot record and give control privilege to boot record. Boot record will let system boot successfully.
Both of them are settings on computer hard ware.How to Clear the CMOS - Reset the BIOS & Why
And setting parameters are saved in CMOS chip.