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From: Alexander Larsson <alla@lysator.liu.se>
To : ggi-develop@eskimo.com
Date: Sun, 05 Jul 1998 19:58:35 +0200
Re: kgicon difficulties |-< (and new tarballs |->)
> Jon writes:
>
> > Today did NOT go as smoothly as yesterday did. I am having
> > problems getting 4bpp modes to work right. The 4bpp routines in fbcon
> > have some major problems, it seems. The foreground color is hardwired to
> > 15, which I found and patched after much head-scratching, but there is
> > still a very strange problem with garbled fonts which I cannot for the
> > life of me track down.
>
> AFAIK (and that aint far), fbcon-cfb4.c is for "4 bit packed pixels"
> which is like the code in lib/libggi/default/linear-4/*, whereas VGA 4
> bit mode is a weird thing called "ModeX" and needs code like the stuff
> in kgi/lib/libggi/IBM/*.
VGA 4-bit mode is not Mode-X. Mode X is a mix of MCGA 256 color mode and the
standard 4-bit vga mode with latches to access the 4 bitplanes.
>
> Also, is the 640x400x4bit mode banked ? It must take up at least 128K,
> but the window at A0000 is usually only 64K (again AFAIK, which aint
> much).
No, 600x400x4 is not banked. At least not in the normal sense. All 4
bitplanes are mapped to the same place in memory and a mask that you can set
decides which bitplane is written to. Soo, it is not 4bit packed but
essentially a 4 bitplane model where the 4 bitplanes are reached in a bit of a
strange way.
/ Alex
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