VGA splitter cables

1 Male to 2 Female VGA Splitter Cable 1.Top quality prod uts and excellent service 2.100% Triple Shield

The VGA specifications are as follows:

256 KB Video RAM (The very first cards could be ordered with 64KB or 128KB of RAM at the cost of losing some video modes). 16-color and 256-color modes 262,144-value color palette (six bits each for red, green, and blue) Selectable 25.175 MHz or 28.322 MHz master clock Maximum of 800 horizontal pixelsMaximum of 600 linesRefresh rates at up to 70 Hz Vertical blank interrupt (Not all clone cards support this.) Planar mode: up to 16 colors (4 bit planes) Packed-pixel mode: 256 colors (Mode 13h) Hardware smooth scrolling support Some "Raster Ops" support Barrel shifter Split screen support 0.7 V peak-to-peak 75 ohm double-terminated impedance (18.7mA – 13 mW)

The VGA supports both All Points Addressable graphics modes, and alphanumeric text modes. Standard graphics modes are:

640×480 in 16 colors 640×350 in 16 colors 320×200 in 16 colors 320×200 in 256 colors (Mode 13h)

As well as the standard modes, VGA can be configured to emulate many of the modes of its predecessors (EGA, CGA, and MDA). Compatibility is almost full at BIOS level, but even at register level, a very high value of compatibility is reached. VGA is not compatible with the special IBM PCjr or HGC video modes.

Signal

The intended value for the horizontal frequency of VGA is exactly double the value used in the NTSC-M video system. The formula for the VGA horizontal frequency is thus (60 ÷ 1001) × 525 kHz = 4500 ÷ 143 kHz ≈ 31.4686 kHz. All other frequencies used by the VGA card are derived from this value by integer multiplication or division. Since the exactness of quartz oscillators is limited, real cards will have slightly higher or lower frequency. For most common VGA mode 640×480 "60 Hz" non-interlaced the horizontal timings are:

ParameterValueUnit

Pixel clock frequency	25.175	MHz
Horizontal pixels	640
Horizontal sync polarity	Negative
Total time for each line	31.77	µs
Front porch (A)	0.94	µs
Sync pulse length (B)	3.77	µs
Back porch (C)	1.89	µs
Active video (D)	25.17	µs

(Total horizontal sync time 6.60 µs)

 

The vertical timings are:

ParameterValueUnit

Vertical lines	480
Vertical sync polarity	Negative
Vertical frequency	59.94	Hz
Front porch (E)	0.35	ms
Sync pulse length (F)	0.06	ms
Back porch (G)	1.02	ms
Active video (H)	15.25	ms

(Total vertical sync time 1.43 ms)

640 × 400 @ 70 Hz is video mode used for booting most x86 personal computers.

640 × 480 @ 60 Hz is the default MS-Windows graphics mode with 16 colors.[7]

The actual timings vary slightly. For example for 640×480 @ 60fps a 25,17 µs active video time with a pixel frequency of 25,174 MHz gives 633 pixels rather than the expected 640 pixels

VGA splitter cables