[Intel-gfx] Sandy Bridge Desktop - 1920x1080i interlace not working

Alfonso Fiore alfonso.fiore at gmail.com
Sun Jan 22 02:55:55 CET 2012

On Sat, Jan 21, 2012 at 10:09 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
> Ok, from the above it looks like the VGA input on your TV is dirt-cheap
> and it barely manages to sync at 800x600 and fails already at 1024x768 -
> not even the bios manages to put a picture on your TV :(
> To make sure that this is not an issue with the intel gpu, can you maybe
> test the vga input with another machine with different gpu?

Hi Daniel,

I used this TV for the last 3 years connecting each and all my laptops
and I never had a problem running 1024x768 with Windows over VGA (as
an extension of my laptop).
However cheap my VGA input might be, Windows handles it just fine.
My current GPU is ATI mobility radeon HD 3400.
If you want, I can try to run Ubuntu from USB on my laptop and see if
Ubuntu can control my monitor over VGA.
Let me know if this test helps at all (I would prefer to skip it if
the info I provided are enough).

I don't have other desktops.
The only box I can try for POST over VGA is an ALIX
(http://pcengines.ch/) and it also doesn't work very well with my TV
but at least it shows a flickering image.

Again, with laptops and Windows it has been running fine for ages over VGA.

Also: I'm sure you are looking at the big picture, but my goal is for
sure HDMI, not VGA.

> The overscan is expected because your other output HDMI is still at
> 1024x768 and hence your desktop is large enough to fit both.
> See the first line starting with "Screen 0:" in the xrandr output for
> current the size of your desktop.

gotcha. Thanks. I didn't know that (but I could have thought about it...)

> Yep, excellent test descriptions! I still need to look at the register
> dumps, but I think another test might be useful:
> Only HDMI with nomodeset, then again grab the intel_reg_dump. Iirc that
> works, so it could be useful to see how the bios sets things up with just
> the hdmi cable.

is there a typo? Or maybe I don't understand what you are asking?
"grab the intel_reg_dump. Iirc that works" ????
is that intel_reg_dumper?

So you want me to run the same script over HDMI (with only HDMI cable)
with nomeset with all the available resolutions?

> Another thing to try with VGA is whether the higher refresh-rate helps.
> You can select that with --rate, i.e.
> xrandr --output VGA1 --mode 1024x768 --rate 60.0

Should I try just with 60? Or also with other values?
Is this test with or without nomodeset (I guess w/o, but better check)?
Only VGA cable? or also HDMI connected? or both cases?

Please detail case conditions.

I'll try maybe tomorrow night.

thank you for your help,

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