Re: Resolution problem with AMD Radeon 5450/6350 and Dell U3011

[Thomas Lübking]

On Dienstag, 30. Oktober 2012 16:14:32 CEST, Johan Mazel wrote:
> 2012/10/31 Alex Deucher <alexdeucher at gmail.com>:
>> On Tue, Oct 30, 2012 at 6:35 AM, Johan Mazel 
>>> Theoretically, the HD5450 is able to display the screen's native
>>> resolution (2560x1600) according to
>>> http://www.amd.com/us/products/desktop/graphics/ati-radeon-hd-3000/hd-3400/Pages/ati-radeon-hd-3400-specifications.aspx
>>> provided that a dual-link DVI cable is used, which is the case.
>>> Unfortunately, the biggest available resolution is 1600x1200 on Debian
>>> Testing and 1920x1200 for Ubuntu 12.10.

>> While the chip is cable of dual link, dual link is only available if
>> the oem wired up a dual link DVI connector on your card.  If the oem
>> used a single link DVI connector, you will be limited to single link
>> DVI.  I suspect that is what's happening.
>> 
>> Alex
>
> Are you sure that this would explain both problems (I mean with Debian
> and Ubuntu) ?
> One hypothesis might be that the package used by Ubuntu 12.10 fixes
> the software problem present in Debian's package version while the
> hardware problems remains...

Single link is limited to 1600x1200 unless the entire chain supports reduced blanking, what bumps the limit to 1920x1200 (both at 60Hz)
Support for latter is probably not correctly detected on the Debian system.

You can use xrandr --newmode and --addmode and see what happens if you try to forcefully select 2560×1600 (but i'd add a "sleep 10; xrandr -s 1920x1200" because the screen will likely turn off - or the DVI link burns ;-)

Also ensure the cable to actually support DL and is not broken (test on other system)

Notice that DVI-D does *not* mean "Dual"-Link, but "Digital". You need the pins in the center:
http://upload.wikimedia.org/wikipedia/commons/thumb/f/fb/DVI_Connector_Types.svg/1000px-DVI_Connector_Types.svg.png

Cheers,
Thomas