Specifications

Figure 15.10 VGA connector used for SVGA and other VGA-based standards.

Table 15.7 Standard 15-Pin VGA Connector Pinout

Pin # Function Direction Pin # Function Direction

1 Red video Out

2Green video Out

3 Blue video Out

4 Monitor ID 2 In

5 TTL Ground (monitor self-test) –

6 Red analog ground –

7Green analog ground –

8 Blue analog ground –

Video Display Adapters

897

SVGA provides capabilities that surpass those offered by the VGA adapter. Unlike the display adapters

discussed so far, SVGA refers not to an adapter that meets a particular specification, but to a group of

adapters that have different capabilities.

For example, one card might offer several resolutions (such as 800×600 and 1024×768) that are greater

than those achieved with a regular VGA, whereas another card might offer the same or even greater

resolutions but also provide more color choices at each resolution. These cards have different capabili-

ties; nonetheless, both are classified as SVGA.

The SVGA cards look much like their VGA counterparts. They have the same connectors, but because

the technical specifications from different SVGA vendors vary tremendously, it is impossible to provide

a definitive technical overview in this book. The connector is shown in Figure 15.10; the pinouts are

shown in Table 15.7.

Chapter 15

11 12 13 14 15

78910

2345

9 Key (plugged hole) –

10 Synch Ground –

11 Monitor ID 0 In

12 Monitor ID 1 In

13 Horizontal Synch Out

14 Vertical Synch Out

15 Monitor ID 3 In

On the VGA cable connector that plugs into your video adapter, pin 9 is often pinless. Pin 5 is used

only for testing purposes, and pin 15 is rarely used; these are often pinless as well. To identify the

type of monitor connected to the system, some manufacturers use the presence or absence of the

monitor ID pins in various combinations.

VESA SVGA Standards

The Video Electronics Standards Association includes members from various companies associated

with PC and computer video products. In October 1989, VESA recognized that programming applica-

tions to support the many SVGA cards on the market was virtually impossible and proposed a stan-

dard for a uniform programmer’s interface for SVGA cards; it is known as the VESA BIOS extension

(VBE). VBE support might be provided through a memory-resident driver (used by older cards) or

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