Bug#529178: video-radeon: Probably hardware limitation

[Alex Deucher]

On Thu, Jul 23, 2009 at 11:10 AM, Michal Suchanek<hramrach at centrum.cz> wrote:
> 2009/7/23 Alex Deucher <alexdeucher at gmail.com>:
>> On Thu, Jul 23, 2009 at 7:47 AM, Michal Suchanek<hramrach at centrum.cz> wrote:
>>> 2009/7/22 Alex Deucher <alexdeucher at gmail.com>:
>>>> On Wed, Jul 22, 2009 at 3:47 PM, Michal Suchanek<hramrach at centrum.cz> wrote:
>>>>> Package: xserver-xorg-video-radeon
>>>>> Followup-For: Bug #529178
>>>>>
>>>>> This is probably a hardware limitation of the card.
>>>>>
>>>>> AFAIK dual-link dvi is needed for modes above 1280x1024 to work reliably
>>>>> over DVI. Some card - monitor combinations might work but others would
>>>>> not.
>>>>>
>>>>> Better cards have higher-rate transmitters that can do modes slightly
>>>>> larger than 1280x1024 but a 22" screen is likely over-spec for any
>>>>> single link card so there is no guarantee it will work.
>>>>
>>>> 165 Mhz is the single link limit.  With reduced blanking you can run
>>>> 1920x1200 at 60Hz.  Most dual link monitors start out around 2560x1600.
>>>>
>>>
>>> Well, reduced blanking is like overclocking. It might work but it might not.
>>>
>>
>> Not exactly.  Lots of monitors (mostly LCDs) require reduced blanking modes.
>>
>>> Either way my experience with Radeon 9250 is that it cannot drive a
>>> 22" screen over DVI reliably, and I read in a bug report somewhere
>>> somebody testing about a dozen cards with similar results.
>>>
>>
>> I can run 1920x1200 reliably on a 9250 here.  I've even run it on a
>> radeon 7000, so the hardware is capable.
>
> It's not like it can never works but depending on the card-monitor
> pair it may work flawlessly, blank sometimes, fail to wake up from
> DPMS sleep states, ...
> The solution was to replace these old cards with newer cards where
> larger screen is used.
>
> Here it does not even have the WorksWithWindowsᵀᴹ property so the
> original ATI drivers fail, too.
> Sure, it's not like the X drivers cannot get better than the original
> drivers. Some S3Trio3D/2X cards that did not work well in windows
> would work with X at higher modes and without glitches.
>
> The results may also vary depending on the memory chips and other
> support chips / included features used by the card maker.
>
> For one, if that's a memory bandwidth problem the frequency and bus
> width of the memory chips used may affect the issue and different card
> models by different manufacturers offer different options.
>
> I am not sure where the TMDS transmitter is already integrated into
> the graphics chipset and where it is an option added by the card
> manufacturer. In the later case the parts used by the card maker may
> also affect the capabilities of the DVI output and cause differences
> between  systems.

The tmds controller is integrated into the chips.  However different
oems use different memory types and configuration so that indeed may
be the problem.  An older low end card with slow memory may not be
able to handle the bandwidth for 2d and 3d and a high res screen.
Still, it might be worth trying the modelines and options I suggested.


Alex