Technical information

CHAPTER 2
Hardware Design
24
Video System
Video Timing 2
Table 2-5 and Figure 2-2 define the video monitors and timings supported by the
Macintosh host computer that are also supported by DOS Compatibility Card. For
the Macintosh monitors that are fixed frequency (the 14-inch and 16-inch monitors), the
VGA controller on the card needs to be configured for this horizontal and vertical
retrace rate.
Note
The DOS Compatibility Card can operate with a 17-inch (or larger)
monitor. If such a large monitor is shared, the user can use the Monitors
control panel to set the display to either 640 by 480 pixels or 832 by 624
pixels. If the large monitor is connected directly to the card, the display
is 640 by 480 pixels.
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Table 2-5 VIdeo timing parameters for supported monitors
Parameter 14-inch RGB 17-inch RGB VGA SVGA
Display size (pixels) 640 by 480 832 by 624 640 by 480 800 by 600
Pixel clock 30.24 MHz 57.28 MHz 25.18 MHz 36.00 MHz
Pixel time 33.07 ns 17.46 ns 39.72 ns 27.78 ns
Line rate 35.00 kHz 49.73 kHz 31.47 kHz 35.16 kHz
Line time 28.57 µ s
(864 pixels)
20.11 µ s
(1152 pixels)
31.78 µ s
(800 pixels)
28.44 µ s
(1024 pixels)
Horizontal active video 640 pixels 832 pixels 640 pixels 800 pixels
Horizontal blanking 224 pixels 320 pixels 160 pixels 224 pixels
Horizontal front porch 64 pixels 32 pixels 16 pixels 16 pixels
Horizontal sync pulse 64 pixels 64 pixels 96 pixels 112 pixels
Horizontal back porch 96 pixels 224 pixels 48 pixels 96 pixels
Frame rate 66.72 Hz 74.55 Hz 59.94 Hz 52.71 Hz
Frame time 15.01 ms
(525 lines)
13.41 ms
(667 lines)
16.68 ms
(525 lines)
18.97 ms
(667 lines)
Vertical active video 480 lines 624 lines 480 lines 600 lines
Vertical blanking 45 lines 43 lines 45 lines 28 lines
Vertical front porch 3 lines 1 line 10 lines 1 line
Vertical sync pulse 3 lines 3 lines 2 lines 4 lines
Vertical back porch 39 lines 39 lines 33 lines 23 lines