There is also extra protection from accidental BIOS rewrites in the form of boot blocks which are protected from accidental overwrite or dual and quad BIOS equipped systems which may, in the event of a crash, use a backup BIOS. Most BIOS implementations are specifically designed to work with a particular computer or motherboard model, by interfacing with various devices that make up the complementary system chipset. Image Credit: Uwe Hermann on Flickr. New standards grafted onto the BIOS are usually without complete public documentation or any BIOS listings. The basic input/output system (BIOS) on a computer is typically stored on a non-volatile microchip called a BIOS chip, which is placed on the motherboard of the computer. If the boot block detects any corruption in the main BIOS, it will typically warn the user that a recovery process must be initiated by booting from removable media (floppy, CD or USB flash drive) so the user can try flashing the BIOS again. A modern Wintel-compatible computer provides a setup routine essentially unchanged in nature from the ROM-resident BIOS setup utilities of the late 1990s; the user can configure hardware options using the keyboard and video display. The BIOS originally proprietary to the IBM PC has been reverse engineered by some companies (such as Phoenix Technologies) looking to create compatible systems.[4]. The motherboard BIOS scans for extension ROMs in a portion of the "upper memory area" (the part of the x86 real-mode address space at and above address 0xA0000) and runs each ROM found, in order. Computers are now coming with UEFI firmware instead of the traditional BIOS, but the same is true for UEFI – it’s low-level system software with a similar role. Then it can replace the BIOS boot process with one of its own, or it can merely modify the boot sequence by inserting its own boot actions into it, by preventing the BIOS from detecting certain devices as bootable, or both. Some servers and workstations use a platform-independent Open Firmware (IEEE-1275) based on the Forth programming language; it is included with Sun's SPARC computers, IBM's RS/6000 line, and other PowerPC systems such as the CHRP motherboards, along with the x86-based OLPC XO-1. For example, some ASUS notebooks included Splashtop OS embedded into their NAND flash memory ICs. A non-disk device such as a network adapter attempts booting by a procedure that is defined by its option ROM or the equivalent integrated into the motherboard BIOS ROM. Because boot programs are always loaded at this fixed address, there is no need for a boot program to be relocatable. On the next screen, click on Restart to enter UEFI Firmware settings on your computer.. 3. In a valid expansion ROM, this signature is followed by a single byte indicating the number of 512-byte blocks the expansion ROM occupies in real memory, and the next byte is the option ROM's entry point (also known as its "entry offset"). The BIOS was hard-coded to boot from the first floppy drive, or, if that failed, the first hard disk. Video BIOS), complementing or replacing the system BIOS code for the given component. The BIOS in modern PCs initializes and tests the system hardware components, and loads a boot loader from a mass storage device which then initializes an operating system. Later computers, including all IBM-compatibles with 80286 CPUs, had a battery-backed nonvolatile BIOS memory (CMOS RAM chip) that held BIOS settings. Top Expert 2015. General Software, which was also acquired by Phoenix in 2007, sold BIOS for embedded systems based on Intel processors. Intel processors have reprogrammable microcode since the P6 microarchitecture. - Another option is a flash BIOS recovery jumper or switch used for BIOS recovery. See this answer for a detailed view of memories used during the booting process. If a user performs a fresh install of Windows, they will need to have possession of both the OEM key (either SLP or COA) and the digital certificate for their SLIC in order to bypass activation. If the system has just been powered up or the reset button was pressed ("cold boot"), the full power-on self-test (POST) is run. In modern computer systems, the BIOS contents are stored on a flash memory chip so that the contents can be rewritten without removing the chip from the motherboard. [16], The BIOS uses the boot devices set in Nonvolatile BIOS memory (CMOS), or, in the earliest PCs, DIP switches. Most BIOS revisions created in 1995 and nearly all BIOS revisions in 1997 supported the year 2000 by setting the century bit automatically when the clock rolled past midnight, 31 December 1999. Mebromi is a trojan which targets computers with AwardBIOS, Microsoft Windows, and antivirus software from two Chinese companies: Rising Antivirus and Jiangmin KV Antivirus. Flash chips are programmed (and re-programmed) in-circuit, while EPROM chips need to be removed from the motherboard for re-programming. [citation needed], As a result, as of 2008, CIH has become essentially harmless, at worst causing annoyance by infecting executable files and triggering antivirus software. These updates can be “flashed” onto the BIOS … Jason Carson Computer Technician. The modern Wintel machine may store the BIOS configuration settings in flash ROM, perhaps the same flash ROM that holds the BIOS itself. The cartridges can also contain other types of ROM modules, such as BASIC programs, that are handled differently. [49][citation needed], The third BIOS virus was a technique called "Persistent BIOS infection." For example, most computers have a hard disk that is bootable, but sometimes there is a removable-media drive that has higher boot priority, so the user can cause a removable disk to be booted. [29][30][31][32] Modern operating systems read the e820 memory map at startup. It loads and executes the first boot software it finds, giving it control of the PC. All Rights Reserved, How to Check Computer Specs in Windows 10, How to Remove Bloatware From Windows 10 PC, How to Setup Chromecast on Android and iPhone, Mac vs PC Comparison: Should You Buy Mac or PC, Kindle E-Reader Comparison | Which Kindle to Buy. [33], After operating systems load, the System Management Mode code is still running in SMRAM. This code verifies if the rest of the BIOS is intact (using hash checksums or other methods) before transferring control to it. [citation needed], Some BIOS implementations allow overclocking, an action in which the CPU is adjusted to a higher clock rate than its manufacturer rating for guaranteed capability. The BIOS settings are stored in the CMOS chip (which is kept powered up via the battery on the motherboard). If you are already logged into your User Account, you can enter … The second BIOS virus was CIH, also known as the "Chernobyl Virus", which was able to erase flash ROM BIOS content on compatible chipsets. In the System Summary section, you should see an item called BIOS Version/Date. Jason Carson Computer Technician. CS:IP always points to physical address 0x07C00. Operation of an IBM-compatible computer system can be completely changed by removing or inserting an adapter card (or a ROM chip) that contains a BIOS extension ROM. computer awareness mcq and computer knowledge questions answers are important in ssc, upsc, ibps and competitive examination and entrance tests, set 1 - question 3416 Systems with later processors provide logic to start running the BIOS from the system ROM. Can anyone tell me where the BIOS Setup and Admin passwords are stored on a Dell Latitude D830 laptop PC? AMD provided product specifications for some chipsets, and Google is sponsoring the project. This program allowed the user to set system configuration options, of the type formerly set using DIP switches, through an interactive menu system controlled through the keyboard. 3.2K views Without reprogrammable microcode, an expensive processor swap would be required;[20] for example, the Pentium FDIV bug became an expensive fiasco for Intel as it required a product recall because the original Pentium processor's defective microcode could not be reprogrammed. Then it locates and runs your boot loader, or loads your operating system directly.The BIOS also provides a simple interface for configuring your computer's hardware. BIOS Meningitis has relatively harmless, compared to a virus like CIH. Easy way to fix these i.e remove them 1) Go into command mode (run as administrator) 2) t It had a century bit which allowed for manually changing the century when the year 2000 happened. BIOS, which stands for Basic Input Output System, is software stored on a small memory chip on the motherboard. When you turn on your computer, the BIOS does several things. This allows easy, end-user updates to the BIOS firmware so new features can be added or bugs can be fixed, but it also creates a possibility for the computer to become infected with BIOS rootkits. The basic input/output system (BIOS) on a computer is typically stored on a non-volatile microchip called a BIOS chip, which is placed on the motherboard of the computer. ROMs could be replaced, but not altered, by users. Since the AT-compatible BIOS ran in Intel real mode, operating systems that ran in protected mode on 286 and later processors required hardware device drivers compatible with protected mode operation to replace BIOS services. The IBM PCjr is unique among PCs in having two ROM cartridge slots on the front. BIOS is the program a computer's microprocessor uses to control the computer's initial boot sequence and hardware initialization. Former vendors include Award Software and Microid Research that were acquired by Phoenix Technologies in 1998; Phoenix later phased out the Award brand name. Since 2019, new Intel platform OEM PCs no longer support the legacy option. A boot menu such as the textual menu of Windows, which allows users to choose an operating system to boot, to boot into the safe mode, or to use the last known good configuration, is displayed through BIOS and receives keyboard input through BIOS.[17]. This is why most BBS compliant PC BIOS implementations will not allow the user to enter the BIOS's user interface until the expansion ROMs have finished executing and registering themselves with the BBS API. Researchers Anibal Sacco[50] and Alfredo Ortega, from Core Security Technologies, demonstrated how to insert malicious code into the decompression routines in the BIOS, allowing for nearly full control of the PC at start-up, even before the operating system is booted. If you are not logged into your User Account, you can enter BIOS or UEFI Settings… Cartridges in these slots map into the same region of the upper memory area used for option ROMs, and the cartridges can contain option ROM modules that the BIOS would recognize. The effect of the publication of the BIOS listings is that anyone can see exactly what a definitive BIOS does and how it does it. ROM BIOS or commonly known as BIOS, is an integral part of a computer. In modern PCs running modern operating systems (such as Windows and Linux) the BIOS interrupt calls is used only during booting and initial loading of operating systems. After replacing a modular hardware component inside computer case, the updated information about specific parameters of the new device can be stored in Boot sequence After completing the initial diagnostics and assigning system resources, the startup BIOS program checks for information about secondary storage devices that might contain the OS. This controller was also assigned the A20 gate function to manage memory above the one-megabyte range; occasionally an upgrade of this "keyboard BIOS" was necessary to take advantage of software that could use upper memory. The chip typically stores as little as 256 bytes of information. With the El Torito optical media boot standard, the optical drive actually emulates a 3.5" high-density floppy disk to the BIOS for boot purposes. Starting in 1998, the BIOS flash moved to the LPC bus, a functional replacement for ISA, following a new standard implementation known as "firmware hub" (FWH). In modern PCs the BIOS is stored in rewritable EEPROM or NOR flash memory, allowing the contents to be replaced and modified. A file containing such contents is sometimes termed "a BIOS image". DL may contain the drive number, as used with INT 13h, of the boot device. Theoretically, you will never be asked for a key to activate your machine. When the computer first boots up, BIOS pulls information from the CMOS chip to understand the hardware settings, time, and anything else that's stored in it. I’ve tested it on several Windows 8 pre-installed machine and have confirmed that the information retrieved within the tool is accurate. SPD and memory timings initialization).[42]:8[43]. As of at least 2015, Apple has removed legacy BIOS support from MacBook Pro computers. This began even in the 1980s under MS-DOS, when programmers observed that using the BIOS video services for graphics display was very slow. Even devices built into the motherboard can behave in this way; their option ROMs can be stored as separate code on the main BIOS flash chip, and upgraded either in tandem with, or separately from, the main BIOS. Although sometimes confused with a Complementary Metal Oxide Semiconductor , the BIOS refers to the firmware on the motherboard while the CMOS is the physical location where the date and system configuration data are stored. Early IBM PCs had a routine in the POST that would download a program into RAM through the keyboard port and run it. In 2017, Intel announced that it would remove legacy BIOS support by 2020. Image Credit: Uwe Hermann on Flickr Power users can copy the necessary certificate files from the OEM image, decode the SLP product key, then perform SLP activation manually. In most modern BIOSes, the boot priority order can be configured by the user. The first one found in the wild was Mebromi, targeting Chinese users. Other alternatives to the functionality of the "Legacy BIOS" in the x86 world include coreboot and libreboot. All memory at and above address 0x00500 can be used by the boot program; it may even overwrite itself. If Ctrl+Alt+Delete was pressed ("warm boot"), a special flag value stored in nonvolatile BIOS memory ("CMOS") tested by the BIOS allows bypass of the lengthy POST and memory detection. EEPROM chip (Electrically Erasable Programmable ROM) - you can modify settings-you can fully update by erasing and rewriting. The key is in the Microsoft Licensing Server, not the BIOS. Operating systems can update main processor microcode also. A BIOS reset will erase BIOS settings and return them to the factory defaults. Since few programs used BASIC in ROM, clone PC makers left it out; then a computer that failed to boot from a disk would display "No ROM BASIC" and halt (in response to INT 18h). Once the system is booted, hardware monitoring and computer fan control is normally done directly by the Hardware Monitor chip itself, which can be a separate chip, interfaced through I²C or SMBus, or come as a part of a Super I/O solution, interfaced through Low Pin Count (LPC). It is a non-volatile firmware which means its settings won’t disappear or change even after power off. - A third option is a backup BIOS in case a BIOS upgrade fails or stalls during the upgrade process. BIOS extension ROMs gain total control of the machine, so they can in fact do anything, and they may never return control to the BIOS that invoked them. Systems with a SLIC can be preactivated with an OEM product key, and they verify an XML formatted OEM certificate against the SLIC in the BIOS as a means of self-activating (see System Locked Preinstallation, SLP). UEFI is a specification which replaces the runtime interface of the legacy BIOS. If your PC is pre-loaded with Windows 8, Windows 8.1 or Windows 10, it is very likely that it supports UEFI. If an expansion ROM wishes to change the way the system boots (such as from a network device or a SCSI adapter for which the BIOS has no driver code) in a cooperative way, it can use the BIOS Boot Specification (BBS) API to register its ability to do so.