TOPIC
This article describes the Power Macintosh computer's AV Video Technologies Card's video output.
DISCUSSION Video and graphic images stored in VRAM may have different color depths. The two images exit VRAM through its serial access memory port and pass to the Sebastian color palette chip. Sebastian provides independent color lookup tables for video and graphics images and mixes them into a single digital RGB data stream. The Sebastian then converts the result into analog RGB video, using internal DAC circuits. Analog RGB data passes to the Mickey encoder chip. Mickey either sends RGB directly to the monitor connector or encodes it into NTSC (National Television Standards Committee primarily used in North America and Japan) or PAL (Phase Alternating Line primarily used outside of North America and Japan) video signals in composite or S-video format and sends it to other connectors located on the card. The Power Macintosh uses the HDI-45 for on board video. It supports a dot clock up to 57 MHz. On AV Power Macintosh computers, the AV card supports a dot clock up to 100 MHz. The AV card has two banks of 80-ns VRAM soldered in, with a total capacity of 2 MB. The AV card contains two identical connectors for video input and output with adapter cables for composite video devices that have RCA connectors, such as television equipment. The AV card can support mixed video and graphics in full 24-bit color on small and medium-sized monitors and in 16-bit or 8-bit color on larger monitors. The color depths (in bits per pixel) available when the AV card drives Apple monitors are listed below: Screen Size Color Depths Monitor type Hor.by Vert. Graphics Graphics/video ------------ ------------ -------- -------------- 12-inch RGB* 512 by 384 32 32/16 560 by 384 32 16/16 13-inch RGB or 640 by 400 32 16/16 12-inch monochrome* 640 by 480 32 16/16 704 by 512 32 16/16 Full-page 640 by 870 8 8/8 monochrome* Full-page RGB 640 by 870 16 8/16* 16-inch RGB* 832 by 624 32 16/16 19-inch RGB 1024 by 768 16 8/8 Two-page 1152 by 870 8 8/8 monochrome Two-page RGB 1152 by 870 16 8/8** VGA* 640 by 480 32 16/16 Super VGA 56 Hz* 800 by 600 32 16/16 Super VGA 72 Hz* 800 by 600 32 16/16 Super VGA 60 Hz 1024 by 768 16 8/8** Super VGA 70 Hz 1024 by 768 16 8/8** NTSC 640 by 480 32 16/16 512 by 384 32 16/16 Convolved NTSC 640 by 480 8 n.a. 512 by 384 8 n.a. PAL 768 by 576 32 16/16 640 by 480 32 16/16 Convolved PAL 768 by 576 8 n.a. 640 by 480 8 n.a. * With a color depth of 16 bits in these configurations, the maximum video window size is limited. If the video window width is 512 pixels or less, the height may be as large as 512 pixels; if the video window width is more than 512 pixels, the height is limited to 340 pixels. ** The 8 bits of video are grayscale. The color depths above are shown as the number of bits in which the color or grayscale value of each pixel can be encoded. |
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| Document Information | |
| Product Area: | Computers |
| Category: | Power Macintosh |
| Sub Category: | General Topics |
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