a silly question....8 bit color supprted in 386 vga?

[Kenji Okamoto okamoto@earth.cias.osakafu-u.ac.jp]

Reply to myself.

> > > 
> > > I'm using et4000, att20C490-85, ics2494a set.
> > > This works fine for 1024x768x1i as I reported.   However, after I set 
> > > my "MACHSPEED VGA 1600" card to 1024x768x8i (14" older display), very
> > > atrange behaviors I'm seen.   8-1/2 runs ok, and displays b/w background
> > > on the display.   Then, I tried New command, and located the terminal
> > > emulater area by mouse, then, nothing came up with.
> > > 
> > > Is the 8 bit color mode is supported on this assembly?
> > > What kinds of colors should I see, if I set it as 1024x768x8?
> > 
> > If I choose 640x480x8, I can see color image....
> 
> Further trying revealed follows:
> 
> conditions:   BIOS shadow is enabled for VGA (C0000-C7FFF).
>              my terminal has only 8MB memory, and older low frequency VGA
>              monitor (up to 45 KHz horizontal frequency).
> 
> 640x480x1:   Of course, no problem.  ^_^
> 640x480x8:   No problem to display color images such as dna.3c, table.3c etc.
> 800x600x8:   no problem for smaller size of color image.  For larger image,
>              9v says "Can't read image".
> 1024x768x1i: every thing works fine without color. :-)
> 1024x768x8i: 8-1/2 comes up, but terminal emulater box cannot be
>              set.   I can see and set only rubberband.  After its setting,
>              it disappeares.
> 
> If BIOS shadow is set disabled, things are miserable, that is controller
> not found.  Even if I set environment variable as /env/vgactl, it goes to
> panic.
> 
> Above observation seems to show me a problem on memory space.  My memory
> setting reported by Plan 9 is as follows:
> 
>     1253 free pages, 5012K bytes, swap 29972K, highwater 248K, headroom 308K.

This has been discussed here, which I've missed to understand.

Adding one line of 
          kernelpercent=40
in plan9.ini solved above problem.   Now, I can see 8 bit color image on
1024x768x8i mode.

Kenji