Talk:Video Graphics Array
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vga cable signaling spec?
Memory base
From the article: the video memory for color mode is mapped at 0xb8000-0xbffff.
I thought VGA graphics memory started at 0xa0000? At least, in linear (320x200x256) mode, where each byte was one pixel? -- pne 05:07, 26 Aug 2004 (UTC)
Answer: In graphics mode yes it's 0xa0000. Colour text mode is "0xb8000". -- Funkymonkey.
What about the VESA standard for successors to VGA?
Feel free to add your own info :) -- Funkymonkey.
- 0xb8000-0xbfff is also used for the old CGA color modes (320x200x4, 640x480x2) and text mode. Everything else (320x200x256, 640x480x16, and the EGA 16-color modes) use 0xa0000-0xaffff. 0xb0000-0xb7fff isn't usually touched by VGAs since it's the MDA text buffer. The VESA extensions to VGA are described over in Super VGA. -lee 17:17, 21 Sep 2004 (UTC)
0xb0000-0xb7fff is a perfectly valid address space for the VGA when operating in a Mono text mode (Mode 7). -- Funkymonkey
Removed 640x400 Mode-X and Direct-X reference
I removed the reference to 800x600 and 640x400 modes, as I'm pretty sure they're not possible using standard VGA hardware. 800x600 maybe at a low refresh rate? Remember the distinction between a clone VGA and a "Super VGA" is blurred, some clone VGA's such as Oak's OTI037 256K VGA were capable of 800x600 I remember. However, this page is about the true blue IBM original.
The main reason these modes should be near impossible (especially 640x400 in 256 colours) on standard VGA hardware is that the video bandwidth (28Mhz max) is too low. Horizontal Scan Rate would be unacceptably low. I'd love to be proved wrong however - if someone can demostrate the CRTC settings for a 640x400 256 colour, or 800x600 mode that would run on an IBM VGA with multisync monitor i'd be interested to see it.
I also removed the reference to the 'Direct-X' term double buffering. Double Buffering has long been used as a term before the introduction of Direct-X. -- Funkymonkey
May 8, 2005 - Hi Funkymonkey! There was an old MS-DOS program "FRACTINT", which claimed to support output resolutions up to 800x600 (16-color) on a true "IBM VGA adapter." Years ago, I fooled around with the program, but on an SVGA adapter, so I can't verify the program's claims. I do remember "ModeX" allowed up to 360x480 (60Hz) without resorting to outrageous refresh-rates -- a handful of MS-DOS games used this mode (my favorite was "Bananoid", a shareware clone of Arkanoid.) http://spanky.triumf.ca/www/fractint/hardware_modes.html#video_notes_anchor
June 8, 2005 - Thanks for the info! I'll have to see if I can get an old copy of FRACTINT (I remember it myself from my college days). Sadly I no longer have a real VGA myself - after my recent move I didn't have space in my new home for all of my stuff, and my old IBM PS/2 50Z was left behind :( I'd like to try this out sometime - the VGA is an amazingly programmable device and it may be so that some kind of very hacked 800x600 mode was possible - although i'd guess it would be stretching the limitations of the bandwidth to the limit! Any VGA gurus have the definitive answer on this? --Funkymonkey