A report on Industry Standard Architecture

One 8-bit and five 16-bit ISA slots on a motherboard
8-bit XT, 16-bit ISA, EISA (top to bottom)
8-bit XT: Adlib FM Sound card
16-bit ISA: Madge 4/16 Mbps Token Ring NIC
16-bit ISA: Ethernet 10Base-5/2 NIC
8-bit XT: US Robotics 56k Modem

16-bit internal bus of IBM PC/AT and similar computers based on the Intel 80286 and its immediate successors during the 1980s.

- Industry Standard Architecture
One 8-bit and five 16-bit ISA slots on a motherboard

30 related topics with Alpha

Overall

Motherboard of a NeXTcube computer (1990). The two large integrated circuits below the middle of the image are the DMA controller (l.) and - unusual - an extra dedicated DMA controller (r.) for the magneto-optical disc used instead of a hard disk drive in the first series of this computer model.

Direct memory access

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Feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU).

Feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU).

Motherboard of a NeXTcube computer (1990). The two large integrated circuits below the middle of the image are the DMA controller (l.) and - unusual - an extra dedicated DMA controller (r.) for the magneto-optical disc used instead of a hard disk drive in the first series of this computer model.
Cache incoherence due to DMA

With the IBM PC/AT, the enhanced AT Bus (more familiarly retronymed as the ISA, or "Industry Standard Architecture") added a second 8237 DMA controller to provide three additional, and as highlighted by resource clashes with the XT's additional expandability over the original PC, much-needed channels (5–7; channel 4 is used as a cascade to the first 8237).

Diagram of a motherboard, which supports many on-board peripheral functions as well as several expansion slots.

Super I/O

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Class of I/O controller integrated circuits that began to be used on personal computer motherboards in the late 1980s, originally as add-in cards, later embedded on the motherboards.

Class of I/O controller integrated circuits that began to be used on personal computer motherboards in the late 1980s, originally as add-in cards, later embedded on the motherboards.

Diagram of a motherboard, which supports many on-board peripheral functions as well as several expansion slots.
ITE Super I/O chip (IT8712F)
SMSC (now Microchip) Super I/O chip (FDC37M813) on IBM motherboard

The original super I/O chips communicated with the central processing unit via the Industry Standard Architecture (ISA) bus.

Low Pin Count interface Winbond chip

Low Pin Count

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Computer bus used on IBM-compatible personal computers to connect low-bandwidth devices to the CPU, such as the BIOS ROM (BIOS ROM was moved to the Serial Peripheral Interface (SPI) bus in 2006 ), "legacy" I/O devices (integrated into Super I/O, Embedded Controller or IPMI chip), and Trusted Platform Module (TPM).

Computer bus used on IBM-compatible personal computers to connect low-bandwidth devices to the CPU, such as the BIOS ROM (BIOS ROM was moved to the Serial Peripheral Interface (SPI) bus in 2006 ), "legacy" I/O devices (integrated into Super I/O, Embedded Controller or IPMI chip), and Trusted Platform Module (TPM).

Low Pin Count interface Winbond chip
Trusted Platform Module installed on a motherboard, and using the LPC bus
A diagram showing the LPC bus connecting the southbridge, the flash ROM, and the Super I/O chip

The LPC bus was introduced by Intel in 1998 as a software-compatible substitute for the Industry Standard Architecture (ISA) bus.

A third-party serial interface card for the Apple II that required cutting and soldering to reconfigure. The user would cut the wire traces between the thinly connected ⧓ triangles at X1 and X3 and solder across the unconnected ◀▶ pads at X2 and X4 located at the center of the card. Once done, reverting the modification was more difficult.

Plug and play

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One with a specification that facilitates the discovery of a hardware component in a system without the need for physical device configuration or user intervention in resolving resource conflicts.

One with a specification that facilitates the discovery of a hardware component in a system without the need for physical device configuration or user intervention in resolving resource conflicts.

A third-party serial interface card for the Apple II that required cutting and soldering to reconfigure. The user would cut the wire traces between the thinly connected ⧓ triangles at X1 and X3 and solder across the unconnected ◀▶ pads at X2 and X4 located at the center of the card. Once done, reverting the modification was more difficult.
A NuBus expansion card without jumpers or DIP switches
An MCA expansion card without jumpers or DIP switches
An example of an ISA interface card with extremely limited interrupt selection options, a common problem on PC ISA interfaces. Kouwell KW-524J dual serial, dual parallel port, 8-bit ISA, manufactured in 1992: * Serial 1: IRQ 3/4/9 * Serial 2: IRQ 3/4/9 * Parallel 1: IRQ 5/7 * Parallel 2: IRQ 5/7 (There is no technical reason why 3,4,5,7,9 cannot all be selectable choices for each port.)

Initially all expansion cards for the IBM PC required physical selection of I/O configuration on the board with jumper straps or DIP switches, but increasingly ISA bus devices were arranged for software configuration.

A pair of AMD BIOS chips for a Dell 310 computer from the 1980s

BIOS

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Firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process (power-on startup).

Firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process (power-on startup).

A pair of AMD BIOS chips for a Dell 310 computer from the 1980s
Boot process
BIOS chips in a Dell 310 that were updated by replacing the chips
Award BIOS setup utility on a standard PC
BIOS replacement kit for a Dell 310 from the late 1980s. Included are two chips, a plastic holder for the chips, and a chip puller.
American Megatrends BIOS 686. This BIOS chip is housed in a PLCC package in a socket.
Compaq Portable 386 BIOS
An American Megatrends BIOS showing an "Intel CPU uCode Loading Error" after a failed attempt to upload microcode patches into the CPU
A detached BIOS chip

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 Industry Standard Architecture (ISA) or Low Pin Count (LPC).

A PCI-104 single-board computer.

PC/104

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Family of embedded computer standards which define both form factors and computer buses by the PC/104 Consortium.

Family of embedded computer standards which define both form factors and computer buses by the PC/104 Consortium.

A PCI-104 single-board computer.

Its name derives from the 104 pins on the interboard connector (ISA) in the original PC/104 specification and has been retained in subsequent revisions, despite changes to connectors.

Closeup of an Intel 8259A IRQ chip from a PC XT.

Intel 8259

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Programmable Interrupt Controller designed for the Intel 8085 and Intel 8086 microprocessors.

Programmable Interrupt Controller designed for the Intel 8085 and Intel 8086 microprocessors.

Closeup of an Intel 8259A IRQ chip from a PC XT.
Pinout
NEC D8259AC, used on the original IBM PC motherboard.

The 8259A was the interrupt controller for the ISA bus in the original IBM PC and IBM PC AT.

Interrupt request (PC architecture)

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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.

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.

Technically these lines are named IR0 through IR7, and the lines on the ISA bus to which they were historically attached are named IRQ0 through IRQ15 (although historically as the number of hardware devices increased, the total possible number of interrupts was increased by means of cascading requests, by making one of the IRQ numbers cascade to another set or sets of numbered IRQs, handled by one or more subsequent controllers).

Mark Dean (computer scientist)

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American inventor and computer engineer.

American inventor and computer engineer.

He developed the ISA bus, and he led a design team for making a one-gigahertz computer processor chip.

A typical north/southbridge layout

Southbridge (computing)

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One of the two chips in the core logic chipset on a personal computer motherboard, the other being the northbridge.

One of the two chips in the core logic chipset on a personal computer motherboard, the other being the northbridge.

A typical north/southbridge layout
IBM T42 laptop motherboard with the following labels: CPU (central processing unit), NB (northbridge), GPU (graphics processing unit), and SB (southbridge)
Diagram of an old motherboard, which supports many on-board peripheral functions as well as several expansion slots.

ISA bus or LPC bridge. ISA slots are no longer provided on more recent motherboards. The LPC bridge provides a data and control path to the super I/O (the normal attachment for the PS/2 keyboard and mouse, parallel port, serial port, IR port, and floppy controller).