[ltp] T30/HV Expansion/Projectors

[Alex Deucher]

On 11/6/05, Atul Chitnis <achitnis@exocore.com> wrote:
> I need to figure this one out:
>
> How does HV Expansion work on a TP?
>
> Does the BIOS create a 1400x1050 extrapolated image and pump that to the
> LCD, so that even if I change my resolution to, say, 1024x768 (to
> accommodate a projector/beamer), it is actually still pumping 100x1050?
>

yes.  the radeon has a radimetric scaling uinit that can scale the
output of the first crtc.

> I have found that some (not all) projectors are happier if I have HV
> Expansion turned off on my T30, but I *also* find something weird:
>
> When I have HV Expansion turned on, setting my display to any resolution
> will still get me a full-screen image on my LCD. That's OK - that's how i=
t
> is supposed to work.
>
> But with HV Expansion turned off, the machine boots correctly with a smal=
l
> central text image (no vga=3D832 in grub.conf), and when X comes up, it
> switches to full screen 1400x1050 mode.
>
> Here is where the weirdness begins - I change resolution (xrandr), and th=
e
> display correctly resizes and shrinks, but then *immediately* expands
> again to fill the full screen! I have to hit Fn-F8 a couple of time befor=
e
> it shrinks to the correct size (unexpanded).
>
> Does anyone know what's going on? This is a TP T30, with FC3, fully
> updated.

The Xorg radeon server always uses the LCD scalar.  There are some
patches around to turn it off.  Alternatively you can use the second
crtc to clone your desktop at whatever resolution you want (mergedfb
clone mode).  In that case a separate crtc controls each output so
they can have different timings etc.

Alex

>
> TIA
>
> Atul