Quad Vid.Txt

Macintosh Quadra Built-In Video There have been quite a few questions in this (and other) news groups concerning the built-in video capabilities of the new Macintosh Quadra 700 and 900. In response to these questions, here is an article which provides an in-depth (and accurate!) description of the Quadra video capabilities. This article discusses a number of general Quadra video topics, details how to wire the video connector sense pins to access all the Quadra's supported video modes, and describes the memory configurations necessary to support each of the video modes at specific pixel depths. (And by the way, since I designed the video hardware for both Mac Quadras, you can be reasonably sure this information is accurate.) [Note: You may want to use a mono-spaced, 10-point font to ensure that that that tables in the following sections are formatted correctly.] General Quadra Video Design Philosophy -------------------------------------- The Quadras were designed with a flexible video hardware section in order to support a wide variety of displays. Since the purchaser of one of these CPUs is paying for a frame buffer on the motherboard (whether (s)he wants it or not), and since the Quadras were designed to be high performance machines, the frame buffer was designed to be both very flexible (to support most displays a user may want to use) and to be relatively high performance (to match the computer's capabilities). Obviously every display made by every 3rd party monitor vendor can't be supported by the onboard video, but the Quadras do support a much wider range of displays at a higher level of performance than any previous Macintosh. The Quadra 700 and 900 support pixel depths ranging from 1 to 32 bits per pixel (bpp), Apple displays ranging from the 512 x 384 12-inch color monitor through the 1152 x 870 21-inch color monitor, pixel clocks ranging from 12 to 100 MHz, and a variety of industry standards such as VGA, SVGA, NTSC, and PAL. The Mac Quadra video port produces RS-343 RGB, and also provides horizontal, vertical and composite sync outputs. Composite or S-video output is not provided, but can be accomplished by use of an external RGB-to-composite encoder. The Quadra 700 and 900 also support Apple convolution for flicker-reduction on interlaced displays (i.e., NTSC and PAL) at up to 8 bpp. The Mac Quadras automatically detect the type of display attached to the video connector via 3 'sense' pins on the video connector. Depending on the wiring of these 3 pins, software in ROM configures the video hardware for one the supported display types. (A full description of sense pin wiring and supported display types follows later in this article.) The Quadra 700/900 provide the highest built-in video performance of any Macintosh CPU to date. In a (very) simplified graphics model, we could say that performance depends on two main factors: processor horsepower and the bandwidth the processor has into frame buffer memory. These machines already…