[9fans] escape from vga hell?

[9fans] escape from vga hell?

[Martin Harriss]

I wonder is it absolutely necessary to have an 8-bit VGA graphic system?  I
know monochrome doesn't work any more, but I wondered if it would be possible
to write a driver for 16-color vga mode.  If this were possible, it would
allow people to bring the system up on just about any hardware.

I might be persuaded to find the time to look at this, but thus far I'm
having trouble getting the system up.  I have a Mach32 which worked very
nicely on the old system, but is no longer supported.  I do have a Mach64,
but it complains thus: "undocumented linear aperture size" when I try to bring
it up.  (2MB on the card, and I never got it working under the 2nd edition
either.)

Martin Harriss

[9fans] Re: escape from vga hell?

[Douglas A. Gwyn]

Martin Harriss wrote:
> ... I wondered if it would be possible to write a driver for
> 16-color vga mode.

Russ and I discussed how this could be done, but somebody has
to *do* it.  It would require two kludges:
	(1) map 8-bit general graphics interface into 4-bit pixels
	(2) provide software cursor

Re: [9fans] escape from vga hell?

[forsyth]

Roger Peppe developed a scheme at VN for Inferno that uses the VESA BIOS
support to put the card into a plausible mode before handing
it over to the graphics system.  It isn't as good as a native driver,
for many reasons, but it did quite well on most recent
PCs we tried.  I expect we'll have a go at making it work with
the new Plan 9.

Charles Forsyth

Re: [9fans] escape from vga hell?

[rsc]

regarding 16-color vga mode:
  Yes, great, do it.  You'll want to map all 16-colors to
  16-bit grey to make things work, but other than that
  I really expect that it should be okay.

  The other issue is reintroducing the software cursor,
  which we haven't done.  It's been easier to just keep
  writing hardware cursor code (it's usually quite small),
  and having the hardware cursor makes debugging the
  VGAs a little easier (when the cursor works and the video
  image is wrong, that means you've messed up the
  memory timings).

regarding the memory aperture:
  Send me your vgainfo.txt and we'll get that aperture
  recognized, at the least.

Russ