Editing Video Graphics Array (section)

==Technical details==
Unlike the cards that preceded it, which used binary [[Transistor–transistor logic|TTL]] signals to interface with a monitor (and also [[Composite video|composite]], in the case of the CGA), the VGA introduced a video interface using pure analog [[Component video#RGB analog component video|RGB signals]], with a range of 0.7 volts peak-to-peak max. In conjunction with a [[Color depth#18-bit|18-bit]] [[RAMDAC]] (6-bit per RGB channel), this produced a color gamut of 262,144 colors.<ref name=":1" /><ref name=":2" /><ref name=":3" /><ref name=":4" />

The original VGA specifications follow:

*Selectable 25.175&nbsp;MHz<ref>{{Cite web|url=http://www.tinyvga.com/vga-timing/640x480@60Hz|title=VGA Signal 640 x 480 @ 60 Hz Industry standard timing|website=www.tinyvga.com}}</ref> or 28.322&nbsp;MHz master pixel clock
*Maximum of 640&nbsp;horizontal [[pixel]]s<ref name="ps2_refman1992">PS/2 Video Subsystem Technical Reference Manual 1992</ref> in graphics mode, and 720 pixels in text mode
*Maximum of 480&nbsp;lines<ref name="ps2_refman1992"/>
*[[Refresh rate]]s at 60 or 70&nbsp;[[Hertz|Hz]]<ref>{{cite web|title=VGA Signal timings|url=http://www.tinyvga.com/vga-timing|url-status=live|archive-url=https://web.archive.org/web/20160620145944/http://tinyvga.com/vga-timing|archive-date=2016-06-20}}</ref>
*[[Vertical blank interrupt]] <small>(Not all [[clone (computing)|clone]] cards support this.)</small>
*[[Planar (computer graphics)|Planar]] mode: up to 16&nbsp;colors <small>(4 [[bit plane]]s)</small>
*Packed-pixel mode: 256&nbsp;colors <small>([[Mode 13h]])</small>
*Hardware [[smooth scrolling]] support
*No [[Blitter]]
**Supports fast data transfers via "VGA latch" registers
*[[Barrel shifter]]
*[[Split screen (video games)|Split screen]] support

===Signal timings===
The intended standard value for the horizontal frequency of VGA's {{resx|640x480}} mode is exactly double the value used in the [[NTSC-M]] video system, as this made it much easier to offer optional [[TV-out]] solutions or external VGA-to-TV converter boxes at the time of VGA's development. It is also at least nominally twice that of CGA, which also supported [[composite monitor]]s.

All ''derived'' VGA timings (i.e. those which use the master 25.175 and 28.322&nbsp;MHz crystals and, to a lesser extent, the nominal 31.469&nbsp;kHz line rate) can be varied by software that bypasses the VGA firmware interface and communicates directly with the VGA hardware, as many MS-DOS based games did. However, only the standard modes, or modes that at least use almost exactly the same H-sync and V-sync timings as one of the standard modes, can be expected to work with the original late-1980s and early-1990s VGA monitors. The use of other timings may in fact damage such monitors and thus was usually avoided by software publishers.

Third-party "multisync" CRT monitors were more flexible, and in combination with "super EGA", VGA, and later SVGA graphics cards using extended modes, could display a much wider range of resolutions and refresh rates at arbitrary sync frequencies and pixel clock rates.

For the most common VGA mode ({{resx|640x480}}, 60&nbsp;Hz, [[progressive scan|non-interlaced]]), the horizontal timings can be found in the HP Super VGA Display Installation Guide and in other places.<ref name="Javier Valcarce timings list">{{cite web|title=Javier Valcarce VGA timings page|url=http://www.javiervalcarce.eu/wiki/VGA_Video_Signal_Format_and_Timing_Specifications|url-status=live|archive-url=https://web.archive.org/web/20150102175843/http://javiervalcarce.eu/wiki/VGA_Video_Signal_Format_and_Timing_Specifications|archive-date=2015-01-02}}</ref><ref>HP D1194A Super VGA Display & HP D1195A Ergonomic Super VGA Display Installation Guide, Hewlett Packard</ref>

===Typical uses of selected modes===
{{See also|Extended Display Identification Data}}
{{anchor|640×400}}
{{resx|640x400}} @ 70&nbsp;Hz is traditionally the video mode used for booting VGA-compatible [[x86]] [[personal computer]]s<ref name="epanorama_net-vga_timing">{{cite web|title=ePanorama.net - Circuits|url=http://www.epanorama.net/documents/pc/vga_timing.html|url-status=live|archive-url=https://web.archive.org/web/20090227050541/http://www.epanorama.net/documents/pc/vga_timing.html|archive-date=2009-02-27}} 090425 epanorama.net</ref> that show a graphical boot screen, while text-mode boot uses {{resx|720x400}} @ 70&nbsp;Hz.

This convention has been eroded in recent years, however, with POST and BIOS screens moving to higher resolutions, taking advantage of [[EDID]] data to match the resolution to a connected monitor.{{Citation needed|date=September 2024}}

{{resx|640x480}} @ 60&nbsp;Hz is the default Windows graphics mode (usually with 16&nbsp;colors),<ref name="epanorama_net-vga_timing" /> up to Windows 2000. It remains an option in XP {{citation needed span|date=September 2024|and later versions}} via the boot menu "low resolution video" option and per-application compatibility mode settings, despite newer versions of Windows now defaulting to {{resx|1024x768}} and generally not allowing any resolution below {{resx|800x600}} to be set.

The need for such a low-quality, universally compatible fallback has diminished since the turn of the millennium, {{clarify span|as VGA-signalling-standard screens or adaptors unable to show anything beyond the original resolutions have become increasingly rare.|date=September 2024}}

{{resx|320x200}} at 70&nbsp;Hz was the most common mode for early 1990s PC games, with pixel-doubling and line-doubling performed in hardware to present a {{resx|640x400}} at 70&nbsp;Hz signal to the monitor.

The [[Windows 9x|Windows 95/98/Me]] [[LOGO.SYS]] boot-up image was 320&nbsp;×&nbsp;400 resolution, displayed with pixel-doubling to present a {{resx|640x400}} at 70&nbsp;Hz signal to the monitor. The 400-line signal was the same as the standard {{resx|80x25}} text mode, which meant that pressing {{#invoke:key|press|Esc}} to return to text mode didn't change the frequency of the video signal, and thus the monitor did not have to resynchronize (which could otherwise have taken several seconds).{{Citation needed|date=September 2024}}