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.
One 8-bit and five 16-bit ISA slots on a motherboard
Cache incoherence due to DMA
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

Users frequently had to configure parameters when adding a new device, such as the IRQ line, I/O address, or DMA channel.

- Industry Standard Architecture

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).

- Direct memory access
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.

5 related topics

Alpha

Intel 8237A-5, used on the original IBM PC motherboard.

Intel 8237

Intel 8237A-5, used on the original IBM PC motherboard.
Pinout

Intel 8237 is a direct memory access (DMA) controller, a part of the MCS 85 microprocessor family.

For example, the PIIX integrated two 8237 controllers for ISA bus DMA.

IBM Personal Computer with keyboard and monitor

IBM Personal Computer

First microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard.

First microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard.

IBM Personal Computer with keyboard and monitor
IBM Personal Computer with keyboard and monitor
Internal view of a PC compatible computer, showing components and layout.
Original IBM Personal Computer motherboard
IBM PC with MDA monitor
IBM Model F keyboard
IBM Personal Computer with IBM CGA monitor (model 5153), IBM PC keyboard, IBM 5152 printer and paper stand. (1988)
The back of a PC, showing the five expansion slots
PC DOS 3.30 running on an IBM PC
Digital Research CP/M-86 Version 1.0 for the IBM PC

The peripheral chips included an Intel 8259 PIC, an Intel 8237 DMA controller, and an Intel 8253 PIT.

IBM referred to these as "I/O slots," but after the expansion of the PC clone industry they became retroactively known as the ISA bus.

Three 5-volt 32-bit PCI expansion slots on a motherboard (PC bracket on left side)

Peripheral Component Interconnect

Local computer bus for attaching hardware devices in a computer and is part of the PCI Local Bus standard.

Local computer bus for attaching hardware devices in a computer and is part of the PCI Local Bus standard.

Three 5-volt 32-bit PCI expansion slots on a motherboard (PC bracket on left side)
A typical 32-bit, 5 V-only PCI card, in this case, a SCSI adapter from Adaptec
A motherboard with two 32-bit PCI slots and two sizes of PCI Express slots
Diagram showing the different key positions for 32-bit and 64-bit PCI cards
A PCI-X Gigabit Ethernet expansion card with both 5 V and 3.3 V support notches, side B toward the camera
A semi-inserted PCI-X card in a 32-bit PCI slot, illustrating the need for the rightmost notch and the extra room on the motherboard to remain backward compatible
64-bit SCSI card working in a 32-bit PCI slot
A Mini PCI slot
Mini PCI Wi-Fi card Type IIIB
PCI-to-MiniPCI converter Type III
MiniPCI and MiniPCI Express cards in comparison
A PCI POST card that displays power-on self-test (POST) numbers during BIOS startup
A full-height bracket
A low profile one

The PCI Local Bus was first implemented in IBM PC compatibles, where it displaced the combination of several slow Industry Standard Architecture (ISA) slots and one fast VESA Local Bus (VLB) slot as the bus configuration.

Mini PCI was added to PCI version 2.2 for use in laptops; it uses a 32-bit, 33 MHz bus with powered connections (3.3 V only; 5 V is limited to 100 mA) and support for bus mastering and DMA.

Multi-I/O-Controller with 1×IDE/SCSI-2/FDD/parallel/2×RS232/Game

VESA Local Bus

Short-lived expansion bus introduced during the i486 generation of x86 IBM-compatible personal computers.

Short-lived expansion bus introduced during the i486 generation of x86 IBM-compatible personal computers.

Multi-I/O-Controller with 1×IDE/SCSI-2/FDD/parallel/2×RS232/Game
An ATI MACH64 SVGA VLB graphics card
Computer motherboard with 7 ISA slots of various feature levels. The top three are 16-bit ISA. The middle three are VLB; 16-bit ISA with the added slot (leftmost brown sections). The bottom (shorter) slot is 8-bit ISA. A card installed in this motherboard would have its mounting bracket on the right, which normally would be the "back" of the computer case.
"VIP" motherboard GA486IM from Gigabyte Technology
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Created by VESA (Video Electronics Standards Association), the VESA Local Bus worked alongside the then-dominant ISA bus to provide a standardized high-speed conduit intended primarily to accelerate video (graphics) operations.

VLB provides a standardized fast path that add-in (video) card makers could tap for greatly accelerated memory-mapped I/O and DMA, while still using the familiar ISA bus to handle basic device duties such as interrupts and port-mapped I/O.

IBM Personal Computer/AT

Released in 1984 as the fourth model in the IBM Personal Computer line, following the IBM PC/XT and its IBM Portable PC variant.

Released in 1984 as the fourth model in the IBM Personal Computer line, following the IBM PC/XT and its IBM Portable PC variant.

The bus also offered fifteen IRQs and seven DMA channels, expanded from eight IRQs and four DMA channels for the PC, achieved by adding another 8259A IRQ controller and another 8237A DMA controller.

The AT bus became the de facto "ISA" (Industry Standard Architecture), while PC XT slots were retroactively named "8-bit ISA".