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Video random-access memory (VRAM) is memory dedicated to storing the image that is displayed on a computer's monitor. Video RAM must be fast enough to supply data to the display electronics at the speed at which the screen is scanned. The VRAM may be dual-ported in order to allow the display electronics and the CPU to access it at the same time.

History

Starting in 1984, early black & white compact Macs (such as the Macintosh 128K, 512K, 512Ke, Plus, SE, and Classic) allocated 21,888 bytes (21.375 KB) of the main RAM for use as video RAM.[1] The Macintosh SE/30, introduced in January 1989, had a separate bank of VRAM with 64 KB dedicated to dual display buffers to minimize screen tearing artifacts.[2][3]

In March 1987, the Macintosh II introduced the use of NuBus video cards which contained their own dedicated video RAM.[4] The Macintosh IIci and IIsi, introduced in September 1989 and October 1990, included on-board video circuitry that used a portion of main RAM as VRAM, like early compact models. However, 8-bit color video on a 640 x 480 display would consume 320 KB of the main RAM. Installing a fast video card on these models can free up RAM and improve video performance.[5][6]

In October 1990, the Macintosh LC was the first model to offer a dedicated VRAM SIMM slot on the logic board, allowing the computer's video RAM to be upgraded to support 16-bit color.[7]

In June 1995, the Power Macintosh 9500 introduced the use of PCI video cards which contained their own dedicated video RAM.[4]

References

  1. ↑ Color Basics by Scott Knaster, Macintosh Programming Secrets, p.99. 1987-11.
  2. ↑ Inside the Macintosh SE, Hardware Secrets. 2013-02-06.
  3. ↑ Technical Note HW14: Macintosh SE/30 Info, Apple Computer. 1989-04-01.
  4. ↑ 4.0 4.1 1995: Clones, the Worst Macs, Pippin, PCI Slots, and CPU Daughter Cards by Daniel Knight, Low End Mac. 1995-12-31.
  5. ↑ Mac IIci, Low End Mac. 1989-09-20.
  6. ↑ Mac IIsi, Low End Mac. 1990-10-15.
  7. ↑ Mac LC, Low End Mac. 1990-10-15.

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