Video random-access memory

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 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. The Macintosh SE/30, introduced in January 1989, had a separate bank of VRAM with 64 KB dedicated to to minimize  artifacts.

In March 1987, the Macintosh II introduced the use of NuBus video cards which contained their own dedicated video RAM. 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.

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

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