Talk:Video Graphics Array

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