Intel 8237

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

Direct memory access controller, a part of the MCS 85 microprocessor family.

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

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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

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

In the original IBM PC (and the follow-up PC/XT), there was only one Intel 8237 DMA controller capable of providing four DMA channels (numbered 0–3).

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.

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

Industry Standard Architecture

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

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

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

It has four DMA channels originally provided by the Intel 8237.

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.

A rare Intel C8086 processor in purple ceramic DIP package with side-brazed pins

Intel 8086

16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released.

16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released.

A rare Intel C8086 processor in purple ceramic DIP package with side-brazed pins
Intel 8086 CPU die image
The 8086 pin assignments in min and max mode
Simplified block diagram over Intel 8088 (a variant of 8086); 1=main & index registers; 2=segment registers and IP; 3=address adder; 4=internal address bus; 5=instruction queue; 6=control unit (very simplified!); 7=bus interface; 8=internal databus; 9=ALU; 10/11/12=external address/data/control bus.

Intel 8237: direct memory access (DMA) controller

An Intel P8085AH-2 processor variant with black plastic and silver pins

Intel 8085

8-bit microprocessor produced by Intel and introduced in March 1976.

8-bit microprocessor produced by Intel and introduced in March 1976.

An Intel P8085AH-2 processor variant with black plastic and silver pins
Intel 8085A CPU die
i8085 microarchitecture
i8085 pinout
AMD Am9085
Mitsubishi M5L8085
NEC μPD8085
NZPP Novosibirsk IM1821VM85 (Soviet Union)
OKI M80C85
Siemens SAB8085
Toshiba TMP8085

8237 – DMA Controller

PCI IDE ISA Xcelerator

Family of Intel southbridge microchips employed in some Intel chipsets.

Family of Intel southbridge microchips employed in some Intel chipsets.

The PIIX integrated an IDE controller with two 8237 DMA controllers, the 8254 PIT, and two 8259 PICs and a PCI to ISA bus bridge.

DOSBox emulates the command-line interface of DOS.

JPC (emulator)

X86 emulator written in pure Java.

X86 emulator written in pure Java.

DOSBox emulates the command-line interface of DOS.

Direct Memory Access Controller (DMA): Intel 8237

Two ATA motherboard sockets on the left, with an ATA connector on the right.

WDMA (computer)

The fastest method used to transfer data between the computer (through the ATA controller) and an ATA device until UDMA.

The fastest method used to transfer data between the computer (through the ATA controller) and an ATA device until UDMA.

Two ATA motherboard sockets on the left, with an ATA connector on the right.

The explanation for the difference between single and multiword DMA can be found in how the Intel 8237 DMA chip works.

Motherboard with NEAT chipset for the Intel 80286

NEAT chipset

4 chip VLSI implementation (including the 82C206 IPC) of the control logic used in the IBM PC compatible PC/AT computers.

4 chip VLSI implementation (including the 82C206 IPC) of the control logic used in the IBM PC compatible PC/AT computers.

Motherboard with NEAT chipset for the Intel 80286

8237 DMA controller