Technical information

CHAPTER 2

Hardware Design

Video System

supports the 14-inch and 17-inch RGB Apple monitors as well as the standard VGA

monitors. Table 2-4 summarizes the monitor sizes and display modes supported by the

DOS Compatibility Card.

Note

Monitors of other sizes can be used on the Macintosh host computer but

cannot be shared by the DOS Compatibility Card.

◆

Monitor Sense Lines 2

Monitor types are sensed by way of sense lines in the video cable. Monitor sense line

settings are stored in the interface IC upon power-up when the card is operating in

dedicated monitor mode. The software reads the sense lines and selects the appropriate

video timings and conﬁgurations for the VGA controller.

The extended encodings are not supported when the PC has a dedicated monitor

because the Pretzel Logic IC is unable to separately drive and read the sense lines. When

using a monitor other than the Macintosh 14-inch RGB monitor, the user is required to

indicate use of a 16-inch RGB monitor or a VGA monitor by a setting in the Monitors

control panel.

Table 2-4

Monitors and display modes

Monitor size Modes supported

Macintosh 14-inch All VGA (modes 0–7, D–13h);

SVGA 640 by 480 pixels (79h)

VGA All VGA (modes 0–7, D–13h);

SVGA 640 by 480 pixels (79h)

SVGA All VGA (modes 0–7, D–13h);

SVGA 640 by 480 pixels (79h) and

800 by 600 pixels (6Ah, 70h)

Macintosh 16-inch All VGA (modes 0–7, D–13h);

SVGA 640 by 480 pixels (79h) and

800 by 600 pixels (6Ah, 70h)

Macintosh 17-inch

multiscan

All VGA (modes 0–7, D–13h);

SVGA 640 by 480 pixels (79h) and

800 by 600 pixels (6Ah, 70h)

Macintosh 20-inch

multiscan

All VGA (modes 0–7, D–13h);

SVGA 640 by 480 pixels (79h) and

800 by 600 pixels (6Ah, 70h)