The Video Graphics Array
standard, commonly known as
VGA, was developed by
IBM and became widely used in
the 1980’s for PC monitor
displays. More common today,
however, are the extensions and
supersets of VGA technology.
VGA itself supports 16 colors at
a resolution of 640x480 or 256
colors at a 320x200 resolution.
The extensions and supersets of
VGA, on the other hand, which
are commonly referred to
collectively as Super VGA (SVGA),
can handle higher color depths
and resolutions starting from
800x600 and are used by
virtually every PC monitor and
graphics card in use today. Be
aware, however, that the phrase
“SVGA Compatible”, as seen on
most of today’s monitors and
graphics cards, is virtually
meaningless in describing
exactly what VGA extension is
being used. In order to achieve
the best possible video
performance, the graphics card
and the monitor must support the
same resolutions, color depths,
and refresh rates, in other
words, they both must use the
same VGA extension. Included
under the SVGA umbrella are the
8514/A superset, the Extended
Graphics Array (XGA), and the
Video Electronics Standards
Association’s (VESA)
VESA Bios Extension (VBE), the
latter being the standard VGA
extension in use today. The
VESA Bios Extension allowed for
a virtual guarantee of software
compatibility in the face of
numerous incompatible VGA
extensions.
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The connection type
commonly used for
VGA and SVGA monitor
cables today is a
15-pin VESA
DDC (PnP)
High Density D-Sub
connector (HD15),
which consists of 3
rows of 5 pins each,
which are thinner
than the normal
D-Sub connectors
(DB). Macintosh
monitors, however,
require a DB15
connector, wherein
the 15-pin layout is
organized in only 2
rows. Following are
the pin assignments
for today’s monitor
cables: |
VGA / SVGA
(HD15) Plug |
| Pin # |
HD15 VESA DDC (PnP) |
| 1 |
Red |
| 2 |
Green
/ Mono |
| 3 |
Blue |
| 4 |
Reserved |
| 5 |
Ground |
| 6 |
Red
Ground |
| 7 |
Green
/ Mono Ground |
| 8 |
Blue
Ground |
| 9 |
+5V
DC |
| 10 |
Sync
Ground |
| 11 |
ID
Bit 0 |
| 12 |
DCC
Serial Data |
| 13 |
Horizontal or Comp. Sync |
| 14 |
Vertical Sync |
| 15 |
DCC
Serial Clock |
* ID Bits optionally input
to the computer
* Serial Clock and Data
Lines are bi-directional
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