Talk:Video Graphics Array

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Comments[edit]

vga cable signaling spec?

  • Off the top of my head, the analog RGB cabling is RS-170 compliant, 75-ohm shielded video cable, and the video itself is referenced to 700 mV peak-to-peak. According to the 1992 IBM VGA/XGA Technical Reference, the H-sync and V-sync are both 5-volt TTL, though those lines are typically run through coaxial cable on better cables as well. The old video ID bits are TTL, too, but they've been replaced by DDC2, which is I2C. -lee (talk) 20:16, 25 November 2015 (UTC)

Add monochrome (1-bit) mode to the standard list?[edit]

I'm going to go and add this, and see if it gets reverted. As far as I know, 640x480 (and possibly 640x400?) with a single bitplane - i.e. classic monochrome - is also a standard VGA resolution. I remember being able to set it... in QBasic, in DOS, in Windows 3.1 and even Win 95 with the standard VGA driver (you know... the one which set the dark colours to be not-quite-primary, but not EGA standard either)... and really, it has to be there as an option, otherwise what do you do if you only have 128k or 64k of RAM onboard? Only use the lower resolutions? In which case why not buy an EGA or MCGA board?

Only 256k allows 640x480 in 16 colours (and 320x480 in 256), even though 64k allows 320x200 in 256.

128k limits you to 640x400 (or 640x350, or 320x480) in 16, 640x200/320x400 in 256, and 640x480 in mono (or potentially 4-colour/4-grey, if anyone had bothered to think about offering it... it might have been available as a hack?)

64k makes 640x480 mono-only, along with 640x400, 640x350 and 320x480 (again, 4-colour is a neglected possibility), with 640x200, 320x400 and 320x240(!) all dropping to 16... 193.63.174.211 (talk) 18:49, 23 January 2012 (UTC)

Right, someone zapped it, but I'm putting it back in. If there's a reason for its removal, please come and argue it out instead of being a silent scalpel-wielding dick. Who the hell is going to buy a graphics board with only 128k of RAM, and 640x480 capability, that doesn't have a mode that grants access to its highest resolution? Mono is a standard VGA mode, just as it was on EGA for the lower-RAM boards.
For that matter, so is 640x400. For a start, if you had said 128k board, it'd be the highest rez you could set which would provide 16 colours, and with the 256k you could have two graphics pages for quicker updates (and indeed it'd also be quicker on the 64k for mono, for the same reason). It gets used for BIOS displays and the like, and there's no reason they wouldn't allow it to be settable on grounds of monitor compatibility or the like because the text mode is also 400 lines. I have video card checking programs that run it, in the middle of 350 and 480 line modes, which means it's part of the standard complement rather than an add-on.
Both mono and 640x400 might have faded almost instantly into obscurity thanks to everyone plumping for the 256k boards off the bat but it doesn't mean they weren't there in the first place.
Or maybe I'm wrong? Bring the evidence. Right now it's uncited vs uncited (though I'm not beyond looking up the modelist). Prove 20+ years of experience is mistaken. 193.63.174.211 (talk) 12:03, 7 November 2012 (UTC)
-drinks own kool aid- ... ok, I DID go look it up, and I'll throw my hands up here: It's not a deadset standard mode, so I will now immediately go delete it.
Monitors support it, software supports it, card and monitor testers use it, but it's not on the default list. Which is totally baffling - it means if you have less than full memory you're basically limited to EGA resolution for colour, meaning they really missed a trick in the specification as there was the chance for even the low-end cards to superceed EGA's abilities - but, there you go. Can't change the facts, even if they're stupid.
However, 640x480 in 2 colours IS on the list, so THAT'S staying. 193.63.174.211 (talk) 12:08, 7 November 2012 (UTC)
I think what you've been saying is quite interesting - why not add it anyway? Instead of listing non-standard monochrome modes, you could say something about how the standard missed out on these modes, so cards with insufficient memory had to add non-standard methods of accessing them. Then you could add some examples and references and it would fit nicely in the article. -- Malvineous (talk) 23:39, 7 November 2012 (UTC)
Sadly, unless someone else has already covered this in an off-wiki article somewhere, that would definitely count as Original Research ... and quite a lot of it too, with the associated workload. Not worth it, and would probably get deleted anyway.
I am now trying to work out exactly what I was trying to say up there, some 18+ months ago... monochrome mode removed, but 640x480 in 2 colours stays? Eh? 2 colours is for all intents and purposes monochrome anyway, just that you can change what each of the colours is (and as that's just tweaking chip registers, it won't use any memory). Did I mean 2 *bitplanes* (so, 4 colours)? A different resolution (640x400 or more likely 640x350 in 2 colours)? Something else entirely? 193.63.174.211 (talk) 12:14, 20 June 2014 (UTC)
VGA supports 640x480 in 16 colors and 2 colors.
640x480 in 2 colors requires 37.5 KB memory (just over 32 KB, so 64 KB is needed)
800x600 in 2 colors requires 58.6 KB memory (that's better fit for 64 KB)
So any color depth that can be saved in 640x480 can also be saved in 800x600 without increasing size of card needed.
I will show overview of different card memory sizes:
KEY MODE: 640x480 monochrome (also 16 colors if possible) (resolution race for larger cards)
256 KB supports 640x480 (also 800x600) 16 colors. Honorable mentions include 1280x800 or 1360x768 (WXGA) in 4 colors and 1920x1080 (full HD) in 2 colors.
128 KB supports 640x480 in 4 colors or 640x400 in 16 colors. Also WXGA in 2 colors.
64 KB supports 640x480 (max 832x624) in 2 colors, but 640x400 in 4 colors.
32 KB supports 640x400 in 2 colors. That's almost enough. 720x350 in 2 colors is also supported.
KEY MODE: Most resolution in 256 colors
256 KB supports 640x400 in 256 colors!
128 KB supports 640x200 or 400x300 in 256 colors. Still good.
64 KB supports 320x200 in 256 colors.
32 KB supports 160x200 in 256 colors. That's similar to CGA problem with 16 color.
16 KB supports 160x100 in 256 colors. Wish CGA had this mode!
KEY MODE: Color depth race
256 KB supports 640x200 in 65536 colors and 320x200 in 4294967296 colors.
128 KB supports 320x200 in 65536 colors and 160x200 in 4294967296 colors.
64 KB supports 160x200 in 65536 colors and 160x100 in 4294967296 colors.
32 KB supports 160x100 in 65536 colors and 80x100 in 4294967296 colors.
16 KB supports 80x100 in 65536 colors. What if CGA had this mode?

217.99.252.102 (talk) 11:28, 27 September 2015 (UTC)

Error in first paragraph[edit]

VGA is analog, but it is not "‎Amplitude Modulated". Modulation requires a carrier which is altered by the modulating signal. VGA is a baseband signal without modulation. — Preceding unsigned comment added by Whitcwa (talkcontribs) 17:36, 29 January 2016 (UTC)

Done (WP:BOLD). "Amplitude modulated" is nonsense for VGA, it would be sort of true for video standards like PAL, NTSC and SECAM, in which the color information is quadrature-amplitude modulated, while the brightness information is transferred in baseband. Greets from the electrical engineering department of ETH Zurich. 129.132.3.139 (talk) 10:04, 2 April 2016 (UTC)

Exact VGA timings[edit]

The expression in the article does imply an exact frequency of 60/1.001, but how is this determined from the rounded numbers in the source or other timings provided through EDID, which I believe are rounded too and don't allow fractional math? Indeed, the microsecond durations seen here appear to have been calculated with these rounded numbers. 83.93.8.224 (talk) 20:10, 27 February 2016 (UTC)

article is aimless tech talk[edit]

the articles speaks continuously of vga modes, but never says the mode number for that mode (or that other modes can change away from vga altogether)

the article gives only a discussion which is useless and cannot be used, the references likewise (no mode numbers, no assembler or C code to operate, and references are wanna-be's - not manufacturer documentation or industry documentation from "the people who adhered to the standard"

a good article (and past apparently deleted content!!!) either:

(1) gives history, associations responsible, location of documentation, uses in industry and home

OR

(2) only says what it intends to describe in a usable manner (ie, with code examples, which many wikipedia articles have)

this appears to be an attack (the direction to this page, the removal of past information) by cheap video card makers WHO DID NOT PUT REAL VGA ON NEWER CARDS TO SAVE MONEY - thus the attack is denial of information and denial it's still "THE STANDARD THAT WORKS MORE WIDELY THAN ANY OTHER TO THIS DAY" — Preceding unsigned comment added by 72.219.207.25 (talk) 02:07, 28 July 2016 (UTC)