Intel 8237

Intel 8237 is a direct memory access (DMA) controller, a part of the MCS 85 microprocessor family. It was used as the DMA controller in the original IBM PC and IBM XT. Later IBM-compatible personal computers may have chip sets that emulate the functions of the 8237 for backward compatibility.

The 8237 DMA controller supplies the memory with control signals and memory address information during the DMA transfer. The 8237 permits high-speed data transfer between memory and the I/O with reduced load on the system main processor.

The 8237 is a four-channel device that can be expanded to include any number of DMA channel inputs, although four channels is common for many small systems. The 8237 is capable of DMA transfers at rates of up to 1.6 MByte per second. Each channel is capable of addressing a full 64k-byte section of memory and can transfer up to 64k bytes with a single programming.