Subject: Re: qtopia
To: Michael Lorenz <>
From: Garrett D'Amore <>
List: tech-kern
Date: 06/03/2006 21:29:33
Michael Lorenz wrote:
> Hello,
> >>>> Except that some of us can't look at CRT displays with refresh rates
> >>>> below 85Hz without seeing 'large area flicker' - which hurts.
> >>> Then you should switch resolution as well.
> >>> On a TFT that doesn't make much sense though and I think we should
> have reasonable support for both cases.
> >>
> >> Well, if the monitor supports certain modes with >=85Hz
> vertrefresh, the display driver should as well (if the RAMDAC supports
> it, that is). On a sidenote, I have my two IIyama VMP454s running at
> 1600x1200x32 @ 100Hz without problem. As for TFTs, I was under the
> impression that the analog refresh rate doesn't matter because the
> internal analog->digital panel converter has no glow decay like a CRT
> (same goes for the refresh rate of a panel connected via DVI btw).
> The point was that it doesn't make sense to switch /resolution/ on a
> TFT so it would make sense to switch colour depth independently.

You wouldn't normally change the resolution of the display, but you
might change the perceived resolution.  This could be done with
ratiometric expansion on the display adapter (e.g. like radeon has), or
it might be done in logic in the display itself (most panels with analog
ports have ratiometric expansion for VGA modes, etc.)

The reason people want to run these panels at lower resolutions:

    * the display adapter might not be capable of driving it at full
resolution (e.g. a 1920 native panel hooked up to a card with only 4MB RAM.)

    * the user wants to use a lower resolution to make text bigger. 
(Yes, the "right" answer is to scale the fonts, but most users -- and
most software! -- lack the savvy to change the displayed font size to
adjust for larger screens, etc.)  This is a very common practice amongst
windows users.

    * you have a high-end panel (like I do) but you need to emulate/test
a lower resolution.

Anyway, even if the physical resolution is fixed, the logical resolution
needs to be able to pan.

Plus you're going to want to adjust *up* to higher resolutions using
panning.  (E.g. using a laptop with an XGA panel, hooked up to an SXGA
or WXGA external screen.)

    -- Garrett
> have fun
> Michael
> -- 
> Garrett D'Amore, Principal Software Engineer
> Tadpole Computer / Computing Technologies Division,
> General Dynamics C4 Systems
> Phone: 951 325-2134  Fax: 951 325-2191