Technical Explanation of AMD DVI Setting?

[Chyrak]

Hello everyone, I have been researching a particular DVI setting in the AMD Catalyst Control Center application known as "Alternate DVI Operation Mode"

Now, The reason for my interest in this setting is because it is always enabled by default upon driver installation if you're using a monitor connected with DVI. But the information bubble for this setting states "Enable this if you're experiencing display corruption on your digital panel"

This got my attention and I started to dig around for answers, I started looking for information about when this setting first appeared in CCC and eventually came across the release notes for catalyst version 02.3 These release notes contain some information about this setting that I don't think many people have seen. Here is the release notes.

Spoiler: CATALYST™ Version 02.3 Web Posting Release Notes

Features of ATI CATALYST™ Version 02.3
• Performance Improvements –As with most CATALYST releases performance has increased in
various situations. Here are some examples observed in CATALYST 02.3:
o NHL 2002 scores are up 10-20% for RADEON 7000/7500/8500/9000 products
o Serious Sam performance is improved once again (8-12%) across all RADEON’s
o NASCAR 2002 performance is up 8% on the RADEON 9700 PRO
o Vertex Shader performance has been improved by approximately 20% for the RADEON 9000
PRO, resulting in a 3-5% gain in 3DMARK score.
• Control Panel support for TRUFORM – TRUFORM is a CATALYST feature which allows
for a higher polygon count, resulting in smoother images in games that support it. The ATI Direct3D
tab and the ATI OpenGL tab now contain two radio buttons allowing TRUFORM to be set Off or to
be enabled via Application Preference
• DVI alternate operation mode – New option found in the Details Tab of the Control Panel for
the RADEON 9700. It allows for the switching of different architectures for the integrated DVI
transmitter. This option should only be enabled if display corruption is being experienced.
• AA and AF - OpenGL and Direct 3D Control Panels for RADEON 7000 and RADEON 7200 now
include Anisotropic Filtering and Anti-Aliasing sliders. These are tied into the main settings slider.
This gives users of these cards even more control over their choice of image quality and
performance.
Color Controls for Component Output – This feature enhancement allows for the user to control
the brightness, Contrast, and Saturation of the YprPb properties. The user can control these options when
an HDTV is connected to the component out, using the ATI HDTV dongle adapter.
Enhance gamma control for overlay – The values of the gamma option found in the ATI Overlay
tab of the Control Panel now reflect real world unit values
Newest member of the RADEON family:
These drivers now fully support the newest members of the ATI RADEON family:
RADEON 7500 PCI version
RADEON 9700 Pro
RADEON 9000 Series
CATALYST CREW Feedback Program
This driver release continues to incorporate suggestions provided through the CATALYST CREW feedback
program. Please refer to http://apps.ati.com/driverfeedback/ and provide us further feedback on CATALYST.
Issues Resolved in CATALYST™ Version 02.3
This section provides a brief description of the issues that are resolved with CATALYST™ version 02.3
• Subsystem ID showed incorrect information under details tab
• Hanging issues with Spider Solitaire under Windows XP
• Hanging issues with Mozilla browser
• Setting the desktop to 1024 X 768 and 32 bpp results in the Flat panel property page not appearing
in the ATI displays tab
• RADEON 9700 Control Panel issues: Settings are applied properly, and Quality/Performance
options of Anisotropic Filtering behaves properly.
Errata:
The SmartGart Control Panel has been disabled in this release. All functions will be greyed out and all features will
appear to be turned off. Despite the appearance from the Control Panel, AGP functions are working fine with this
driver. The Control Panel will be enabled in the next driver release.
ATI CATALYST Display Drivers:
The latest ATI display driver provides users with a stable, user-friendly, and flexible software experience.
From supporting the latest 3D architecture and features, to full multimedia acceleration and DVD playback:
The latest ATI display driver will provide users with the ultimate in graphics acceleration.
Direct 3D API graphics acceleration support
Direct 3D acceleration includes support of all the latest features found in the Direct 3D specification. This
allows CATALYST to accelerate the latest amazing 3D graphics effects found in the most popular games.
OpenGL API graphics acceleration support
OpenGL acceleration includes support of all the latest features found in the OpenGL specification. This
allows CATALYST to accelerate the latest amazing 3D graphics effects found in the most popular games.
Amazing Performance
The latest ATI control panel for both D3D and OpenGL provide users with the ability to select a high
performance user experience by enabling “High Performance” textures, and “High Performance” mipmap
detail levels.
TRUFORM™
ATI presents TRUFORM™, the revolution of graphic technology. TRUFORM™, a new technology
developed by ATI, overcomes traditional memory and bandwidth problems to deliver the smoothest and
most realistic images ever seen on a PC. Pre-processes 3D artwork being fed into the graphics accelerator
by converting it from flat triangle data into curved surface data, allowing much more highly detailed and
realistically lit images with virtually no performance loss.
SMARTSHADER™
SMARTSHADER™, a new technology developed by ATI, represents a new generation of visual effects for
your personal computer. With SMARTSHADER™, game developers will be able to create impressive, lifelike
worlds by modeling the surface and material qualities of 3D objects with an unparalleled level of
realism.
This technology revolutionizes the graphics pipeline by making both the geometry processing and pixel
processing stages more programmable than ever before, and allowing developers to easily create amazing
new graphics effects while maintaining a high level of performance.
SMOOTHVISION™
SMOOTHVISION supports a High-Performance anti-aliasing mode and a High-Quality anti-aliasing mode.
Both of these modes give users the ability to choose between 2x, 3x, 4x, 5x, and 6x sampling, allowing for a
total of 10 different anti-aliasing settings.
This allows users to quite easily select both the desired level of visual quality and the corresponding
performance level.
Anisotropic Filtering
Improves image quality by blending multiple texture samples together, resulting in 3D scenes that are crisp
and detailed. The number of samples used can be: 2, 4, 8, or 16. 16X Anisotropic Filtering provides the
ultimate in texture fidelity and detail, while maintaining an incredible level of performance.
SMARTGART™
ATI’s proprietary diagnostic tool to determine the most stable AGP setting, making the most stable drivers in
the industry even more stable.
SMARTGART™ automatically tests the AGP compatibility upon the initialization of the display driver, and
dynamically determines the proper AGP bus speed based on the results of the test. If a new AGP setting is
required and the system must reboot, the driver will automatically set the new bus speed on the next reboot.
The diagnostic tests will only be run on the system when the driver is installed for the first time, or when the
system configuration is changed.

Now, Here is the important bit.
• DVI alternate operation mode – New option found in the Details Tab of the Control Panel for
the RADEON 9700. It allows for the switching of different architectures for the integrated DVI
transmitter. This option should only be enabled if display corruption is being experienced.

The problem on the 9700 card was because of display corruption people were experiencing when using a DVI monitor with this card. Which I think was related to interference on the transmitter itself when a heavy 3D load was running on the card. Which this setting seemed to remedy completely.

From all the information I have been able to gather it seems this option was a work-around for the 9700 to fix some display corruption problems people were having back then with DVI signals, Artifacts and such on this particular model of card.

I have also come across various posts stating that this setting enables "Coherent Mode" on the DVI Transmitter which all point to the same source which is a forum post from ToastyX, This information seems to be thrown around a lot when people have asked about this setting but nobody has ever shown proof or any sort of evidence that this does in fact turn on coherent mode.

I was always under the impression that the Monitor and GFX card automatically decides which setting to use Coherent or non Coherent during the initialization stage of the PC(POST) Because of this I don't believe this setting is related to coherent mode. For example if you're monitor required that this specific setting needed to be disabled because your monitor could only accept a non coherent signal then you wouldn't even have a signal on the BIOS screen. Besides the graphics drivers are not even loaded until your OS is booting. So it wouldn't make sense for AMD to have this setting as driver depended. I am almost certain that the DVI transmitter automatically sets this up via hardware negotiation with the monitor as soon as the PC is powered on.


From my own testing it seems that my monitor 120hz panel Dual Link DVI performs better with this setting switched "OFF" The mouse seems to move around the screen smoother and feels more responsive. It also seems that detailed images are easier to make out during motion, Even more apparent on images with bright colors. Although the difference is very minimal.

I have come up with the following theories about this setting.

• It is kind of like the setting (Spread Spectrum) on motherboards which helps to eliminate (EMI) This would explain why it fixed the interference issues on the 9700
• It sacrifices the DVI outputs quality in an almost unnoticeable way in order to work around DVI bandwidth issues by lowering the Pixel Clock the same way reduced blanking does.
• This setting was only needed for the 9700 ATI card a long time ago to fix a specific bandwidth/Interference issue on the 9700 and AMD have just left it in the drivers enabled by default ever since and this setting is no longer needed with modern card/screens.

So what do you guys think about all this? Is there anyone around with deep knowledge of AMD drivers that has any insight on this setting?

I really want to get to the bottom of this. If any of you are using DVI monitors, Can you please test how your screen behaves once you have switched this setting OFF.
It can be found under "My Digital Flat Panels">"Properties Digital Flat Panel" It's the setting right at the bottom.

Spoiler: The setting is here

Hope you all had a great halloween!

 

[jboydgolfer]

im on DVI, ill try it..gimme a minute. im assuming ill need to restart after changing it , right?
mine was disabled, by default, atleast i don't recall changing it..turning this on didn't seem to make a noticeable difference, atleast to me.

 

[manofthem]

Just looked at it. It was ticked on by default, so I moved the mouse around, moved some windows around, etc. Then unticked it, did the same. Honestly, there didn't seem to be a noticeable difference right away. I'm leaving it unticked for now and will give it a go to see how it works out.

 

[Mussels]

pretty sure it drops the pixel clock rate, doubt it has any quality effects at all on most monitors.

 

[Chyrak]

im on DVI, ill try it..gimme a minute. im assuming ill need to restart after changing it , right?
mine was disabled, by default, atleast i don't recall changing it..turning this on didn't seem to make a noticeable difference, atleast to me.

I think the setting applies immediately as it seems to cause the monitor to reconnect when it is changed.

Just looked at it. It was ticked on by default, so I moved the mouse around, moved some windows around, etc. Then unticked it, did the same. Honestly, there didn't seem to be a noticeable difference right away. I'm leaving it unticked for now and will give it a go to see how it works out.

If you're feeling up to it this http://testufo.com/#test=photo&photo=quebec.jpg&pps=960&pursuit=0&height=0 has various tests you could try with the options on and off to see if you can perceive any noticeable difference, The moving photo test seems to have the biggest difference for me.
Another thing I'm looking into is if this setting has any effect on screen tearing, Playing around with a few games with vsync disabled I haven't noticed much of a difference though.

 

[FordGT90Concept]

pretty sure it drops the pixel clock rate, doubt it has any quality effects at all on most monitors.

There is a separate checkbox for that.

I have no idea what the "alternate" is.

 

[Ja.KooLit]

subbed. wanna know more about this

 

[OneMoar]

it just relaxes the display timing a bit
was needed for early DVI panels or long cables
its nothing but a throwback these days

 

[FordGT90Concept]

Maybe it has to do with Gamma/CRT support (section 2.2.7):
http://www.cs.unc.edu/~stc/FAQs/Video/dvi_spec-V1_0.pdf

...it is recommended as a default position, that digital monitors of all types support a color transfer function similar to analog CRT monitors (gamma = 2.2) which make up the majority of the computer display market. This will avoid, to a great extent, poor color representations on digital monitors, and the necessity of graphics controllers supporting alternate transfer functions.

It could also be related to the monitor scalar (section 2.2.8.1):

To eliminate the potential for cascaded scalars, if the system scales the image then the system must scale the image to the monitor's defined preferred mode of timing (native pixel format in a fixed pixel format panel).

I think the only way to get a definitive answer is to contact AMD technical support.

 

[Chyrak]

Ok, After testing this with a week playing various different types of games. I have come to the conclusion that this setting should be disabled if your monitor behaves normally with it off. Any modern monitor and graphics cards should have no problem.
This was obviously left in for legacy compatibility reasons and is no longer needed.

The only visual difference I experience with this disabled is being able to make out detail in fast moving images better that have bright colors.
I did submit a technical service request ticket with questions regarding this option but only received a reply asking me to try a different DVI cable even though I explained that I only wanted information about weather it was needed with modern displays. Maybe someone else will have better luck contacting AMD via twitter(I don't use it).

 

[CaSsErDoDo]

I had been dealing with one problem for months because of this setting. My problem was when I got high frame rate and even frametimes my gameplay wasn't smooth and had been like 20-25fps all time! Even windows interface wasn't smooth! That thing was driving me crazy and I couldn't find any solutions with ANYTHING except this setting. I tried everything : Vsync options , multiple windows version (8.1 and 10) , framecaping options (riva tuner-amd driver capping) , Radeonpro settings and much more thing that I dont remember now. Today this setting drew my attention and wanted to try. I didnt have anything to lose. After unticked it and magic happened. Windows 8.1 interface now acting snappier and Battlefield 4... My god that is fantastic. All that vivid colors and brightness with smooth play exactly what I am searching for months. On other games camera movements act like exactly what it should. I am following this website for years but have not thougth to register for its forum. But this thread and its comments saved me from buying another monitor. Also gave me a little bit deeper knowledge Thank you Chyrak and other members to contribute with its comments. Thank you.

My Monitor : Samsung 2233BW using with dual-link dvi cable.
Graphic Card : Asus R9 280 Direct CUII TOP
Driver : AMD 16.5.3