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"DMA" redirects here. Not to be confused with the European Union's Digital Markets Act.

Direct memory access (DMA) is a facility of some architectures which allows a peripheral to read and write memory without intervention by the CPU. DMA is a limited form of bus mastering.[1]

History

The first computer to adopt memory input/output (I/O) principles that would later become known as DMA was the IBM 709, which was introduced in 1958.[2] Early versions of DMA relied on basic block transfer mechanisms to transfer information between computers and memory. However, with the integration of the personal computer in the 1980s, DMA became more common as it had to accommodate the demand of more peripherals connected to a PC. Furthermore, in the 1990s, the rise of the Internet and instant online communication meant the adaptation of DMA was driven even faster.[3]

As bus architecture improved, DMA technology further advanced, and with the proliferation of multi-core processor frameworks and the Internet of Things (IoT), DMA has since become more integrated in computational advancement.[3]

DMA usage by Apple

Early Apple series computers relied on the 1MHz 6502 processor for virtually all tasks involving memory. This would pre-occupy the CPU during data-intensive tasks, such as transferring data into RAM from higher-capacity media, such as disk drives. The Apple II, released in 1977, supported DMA access through its 8 expansion slots.[4] The first card for the Apple II series from Apple Computer with a DMA controller was the Apple II High-Speed SCSI Card, released in 1990.[5]

The Apple Lisa was a dramatic new design that was released in January 1983 with a DMA controller.[6] However, at a list price of US$9,995, it was very expensive and short lived.[7]

The simpler Macintosh 128K was released a year later in January 1984 and used DMA principles in its sound and display circuitry, where audio and video access from memory was interleaved at the frequency of the horizonal video refresh rate, which was 22,254.55 Hz. This set the frequency of 8-bit audio files used by early compact Mac computers.[8] The Macintosh IIfx was released in 1990 with the first dedicated DMA controller for its SCSI bus, resulting in faster data transfers to and from hard disk drives.[9] Since 2012, Mac computers have implemented protected DMA for platform security and to reduce vulnerability. Apple Silicon systems on chip contain an Input/Output Memory Management Unit (IOMMU) for DMA processes involving PCIe and Thunderbolt.[10]

DMA types

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References

  1. ↑ Direct Memory Access at the Free On-Line Dictionary Of Computing. 1996-08-23.
  2. ↑ DMA - A Little Help From My Friends by Andrei Chichak, Embedded. 2017-02-22.
  3. ↑ 3.0 3.1 3.2 What Is Direct Memory Access (DMA)? Meaning, Types, Principles, Working, and Benefits by Chiradeep BasuMallick, Spiceworks. 2024-03-14.
  4. ↑ System Description: The Apple-II by Stephen Wozniak, BYTE / Information Week. 1977-05 / 2012-05-14.
  5. ↑ Apple II High-Speed SCSI Card Owner's Guide (PDF) by Apple Computer. 1990. Archived by Apple IIGS France.
  6. ↑ Lisa Hardware Manual (PDF), Apple Computer Inc. 1985-10.
  7. ↑ The Lisa Was Apple’s Best Failure by Hansen Hsu, IEEE Spectrum. 2023-01-19.
  8. ↑ Inside the Original Macintosh by Daniel Knight, Low End Mac. 2014-01-24.
  9. ↑ Macintosh IIfx Overview (PDF), Apple Computer, Inc. 1990.
  10. ↑ Direct memory access protections for Mac computers, Apple Support. 2021-02-18.
  11. ↑ Direct Memory Access (DMA) Controller in Computer Architecture by Ezekiel Nyamu, Scribd. 2023-07-18.
  12. ↑ Direct Memory Access (DMA) Controller in Computer Architecture GeeksforGeeks. 2023-07-18.

External links

FOLDOC logo This page uses GFDL licensed content from the Free On-line Dictionary of Computing.