In computing, BIOS is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process. The BIOS firmware comes pre-installed on an IBM PC or IBM PC compatible's system board and exists in some UEFI-based systems to maintain compatibility with operating systems that do not support UEFI native operation. The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS originally proprietary to the IBM PC has been reverse engineered by some companies looking to create compatible systems. The interface of that original system serves as a de facto standard.
The Intel 80286 is a 16-bit microprocessor that was introduced on February 1, 1982. It was the first 8086-based CPU with separate, non-multiplexed address and data buses and also the first with memory management and wide protection abilities. The 80286 used approximately 134,000 transistors in its original nMOS (HMOS) incarnation and, just like the contemporary 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088 processors.
The Intel 80186, also known as the iAPX 186, or just 186, is a microprocessor and microcontroller introduced in 1982. It was based on the Intel 8086 and, like it, had a 16-bit external data bus multiplexed with a 20-bit address bus.
In digital computers, an interrupt is a request for the processor to interrupt currently executing code, so that the event can be processed in a timely manner. If the request is accepted, the processor will suspend its current activities, save its state, and execute a function called an interrupt handler to deal with the event. This interruption is often temporary, allowing the software to resume normal activities after the interrupt handler finishes, although the interrupt could instead indicate a fatal error.
A motherboard is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use.
Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU).
The MCS-48 microcontroller series, Intel's first microcontroller, was originally released in 1976. Its first members were 8048, 8035 and 8748. The 8048 is arguably the most prominent member of the family. Initially, this family was produced using NMOS technology. In the early 1980s, it became available in CMOS technology. It was manufactured into the 1990s to support older designs that still used it.
Real mode, also called real address mode, is an operating mode of all x86-compatible CPUs. The mode gets its name from the fact that addresses in real mode always correspond to real locations in memory. Real mode is characterized by a 20-bit segmented memory address space and unlimited direct software access to all addressable memory, I/O addresses and peripheral hardware. Real mode provides no support for memory protection, multitasking, or code privilege levels.
The Intel 8085 ("eighty-eighty-five") is an 8-bit microprocessor produced by Intel and introduced in March 1976. It is the last 8-bit microprocessor developed by Intel.
In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as segmentation, virtual memory, paging and safe multi-tasking designed to increase an operating system's control over application software.
The A20, or address line 20, is one of the electrical lines that make up the system bus of an x86-based computer system. The A20 line in particular is used to transmit the 21st bit on the address bus.
In-circuit emulation (ICE) is the use of a hardware device or in-circuit emulator used to debug the software of an embedded system. It operates by using a processor with the additional ability to support debugging operations, as well as to carry out the main function of the system. Particularly for older systems, with limited processors, this usually involved replacing the processor temporarily with a hardware emulator: a more powerful although more expensive version. It was historically in the form of bond-out processor which has many internal signals brought out for the purpose of debugging. These signals provide information about the state of the processor.
On the x86 computer architecture, a triple fault is a special kind of exception generated by the CPU when an exception occurs while the CPU is trying to invoke the double fault exception handler, which itself handles exceptions occurring while trying to invoke a regular exception handler.
In IBM PC compatible computing, DOS memory management refers to software and techniques employed to give applications access to more than 640 kibibytes (KiB) of "conventional memory". The 640 KiB limit was specific to the IBM PC and close compatibles; other machines running MS-DOS had different limits, for example the Apricot PC could have up to 768 KiB and the Sirius Victor 9000, 896 KiB. Memory management on the IBM family was made complex by the need to maintain backward compatibility to the original PC design and real-mode DOS, while allowing computer users to take advantage of large amounts of low-cost memory and new generations of processors. Since DOS has given way to Microsoft Windows and other 32-bit operating systems not restricted by the original arbitrary 640 KiB limit of the IBM PC, managing the memory of a personal computer no longer requires the user to manually manipulate internal settings and parameters of the system.
BIOS implementations provide interrupts that can be invoked by operating systems and application programs to use the facilities of the firmware on IBM PC compatible computers. Traditionally, BIOS calls are mainly used by DOS programs and some other software such as boot loaders. BIOS runs in the real address mode of the x86 CPU, so programs that call BIOS either must also run in real mode or must switch from protected mode to real mode before calling BIOS and then switching back again. For this reason, modern operating systems that use the CPU in Protected mode or Long mode generally do not use the BIOS interrupt calls to support system functions, although they use the BIOS interrupt calls to probe and initialize hardware during booting. Real mode has the 1MB memory limitation, modern boot loaders use the unreal mode or protected mode to access up to 4GB memory.
In a computer, an interrupt request is a hardware signal sent to the processor that temporarily stops a running program and allows a special program, an interrupt handler, to run instead. Hardware interrupts are used to handle events such as receiving data from a modem or network card, key presses, or mouse movements.
The PS/2 port is a 6-pin mini-DIN connector used for connecting keyboards and mice to a PC compatible computer system. Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. The PS/2 mouse connector generally replaced the older DE-9 RS-232 "serial mouse" connector, while the PS/2 keyboard connector replaced the larger 5-pin/180° DIN connector used in the IBM PC/AT design. The PS/2 keyboard port is electrically and logically identical to the IBM AT keyboard port, differing only in the type of electrical connector used. The PS/2 platform introduced a second port with the same design as the keyboard port for use to connect a mouse; thus the PS/2-style keyboard and mouse interfaces are electrically similar and employ the same communication protocol. However, unlike the otherwise similar Apple Desktop Bus connector used by Apple, a given system's keyboard and mouse port may not be interchangeable since the two devices use different sets of commands and the device drivers generally are hard-coded to communicate with each device at the address of the port that is conventionally assigned to that device.
System Management Mode is an operating mode of x86 central processor units (CPUs) in which all normal execution, including the operating system, is suspended. An alternate software system which usually resides in the computer's firmware, or a hardware-assisted debugger, is then executed with high privileges.
The Intel 8255 Programmable Peripheral Interface (PPI) chip was developed and manufactured by Intel in the first half of the 1970s for the Intel 8080 microprocessor. The 8255 provides 24 parallel input/output lines with a variety of programmable operating modes.
An Embedded Controller (EC) is a microcontroller in computers that handles various system tasks. Now it is usually merged with Super I/O, especially on mobile platforms.
