Re: CVS updates/VGA mode setting

[Vojtech P. <vo...@su...>]

On Thu, Aug 31, 2000 at 11:30:04PM +0000, Petr Vandrovec wrote:
> On 31 Aug 00 at 23:01, Vojtech Pavlik wrote:
> > On Thu, Aug 31, 2000 at 06:36:08PM +0000, Petr Vandrovec wrote:
> > 
> > > If you want to support only standard modes (text, cfb8, vgaplanes, 
> > > vga8planes), it is easy. But there is couple of more or less nonstandard
> > > modes too. 2 (1plane) or 4-color (2planes) modes, alphanumeric mode with
> > > character generator disabled (gives you `spectrum like' attribute + 8pixels).
> > > What to do with them? Let them fall through and report something similar
> > > for them?
> > 
> > The 1-line font (which you describe as spectrum-like) actually could be
> > quite useful for having a huge font, while still keeping minimum video
> > memory size.
> 
> Problem is that standard VGA can use only 64KB (VGA text compat.),
> or 128KB (when VGA hardware in real 4plane mode) in that mode, as planes
> 2 & 3 are reserved for character generator and unused... This
> limits you to either 80x409 (~ 640x409) or 80x819 (or 100x655 (~800x655))... 

This is just fine for 80x25 text w/ unlimited font ... (80x25 is
720x400, assuming 9-bit mode).

> This is not too much - it is same as 4plane modes (real textmode with
> 8x16 font gives you virtual screen 640x6544, BTW).
> 
> And unfortunately, although bmove works on same speed as in 4plane mode,
> putc/putcs are much slower, as you cannot use special VGA write modes :-(
> 16 writes in 128KB mode, instead of 8 for 4plane...
>                                                  Best regards,
>                                                     Petr Vandrovec
>                                                     van...@vc...
>                                                     

-- 
Vojtech Pavlik
SuSE Labs