6 Replies Latest reply on Aug 13, 2014 4:51 AM by SGYM

    Dithering on iGPUs


      Hi everybody,


      Yesterday I got myself a new laptop with Core i7 / nVidia GT630M combo. Before this I had Core i5 / ATi 5850HD combo. First thing I noticed were the almost transparent vertical lines on the screen - I've seen them before on my old laptop when Intel iGPU was selected in Hybrid graphics settings. Selecting ATi card resulted in perfectly normal output picture. So I tried to force nVidia GPU and apparently you cannot do that with nVidia since even when the proper GPU kicks in the image is fed to the display by iGPU.


      So I went on Google and after a few hours found the exact description of the problem: dithering issue with Intel's iGPUs: http://forums.macrumors.com/showthread.php?t=905151&page=3


      It has been there since first iGPUs and Intel never seemed to care. But now that I cannot force a proper GPU in the settings I would like Intel to notice this really annoying issue and release a solution.


      The page to test the picture: Black level - Lagom LCD test


      It looks a lot like static dithering example from that page except for it is vertical and shows up every 5 pixels or so. I used to think it was a display issue or something wrong with my particular iGPU on the old laptop, but now I've got 2 laptops with iGPUs with release dates separated by 3 years and I'm pretty sure it's something with either Intel's drivers or the hardware design.


      Connecting another external display to VGA slot does not result in any similar issues on it.


      Tech details:

      Old laptop with same issue: Acer Aspire 7745G, Core i5 450M + Radeon HD 5850, Win7 SP1 x64

      New laptop same issue: Dell Inspiron 17R 5720, Core i7 3612QM + GeForce GT 630M, Win7 SP1 x64

      Latest drivers in both cases, that is.


      I will be happy to provide any further details and cooperation as long as this issue gets noticed by the devs.




        • 1. Re: Dithering on iGPUs



          It looks like your system is currently running switchable graphics; this means that your computer runs Intel graphics and Nvidia at same time. This type of computers do not use generic Intel drivers, they require special drivers from the computer manufacturer. I would highly recommend you contact your computer manufacturer for further assistance.




          • 2. Re: Dithering on iGPUs

            Hi Allan,


            Done that with no success: [Inspiron 17R] How do I completely disable iGPU? - Laptop Video Forum - Laptop - Dell Community


            I have tried all kinds of drivers: from laptop manufacturer, from Intel, from nVidia even the Beta drivers. None of them allow me to completely disable iGPU on Intel/nVidia combo and there is no such option in BIOS (there was one on Intel/AMD).


            I have sent a request to replace my laptop with another one that has AMD graphics but in Estonia (where I am currently located) that is a long shot - our resellers tend to screw people over when replacing/returning/repairing things. Will never buy or advice my friends to buy a laptop with Intel or nVidia graphics, that is for sure.


            More technical description of the problem: Intel's iGPU does not render output properly for 6-bit displays, which results in static dithering and colour banding artifacts. Given the fact that most laptops have 6-bit built-in displays, this problem must be very common, it makes me wonder why there is no scandal about this yet.




            • 3. Re: Dithering on iGPUs

              Update, just got a reply from our Dell reseller, they told me they don't accept returns/don't do replacements/to generally f*** off when you buy something on the account of your company, so Intel, you're my only hope

              • 4. Re: Dithering on iGPUs

                The issue is still here with all the newest updates. Terrible banding and dithering on built in LCD, perfectly normal picture on external monitors.

                • 5. Re: Dithering on iGPUs

                  The iGPU is the primary video adapter which is i2c-associated/hardwired with the internal panel and the NVidia GPU only acts as an accelerator for certain power hungry applications therefore the NVidia GPU might be unable to directly access the internal panel. To clear on the dithering, most of internal panels don't have built-in image processing chipsets and the only input they offer is mostly 8-bit or 6-bit color depth depending on the GPU for dithering and scaling. The main GPU manufacturers use the following dithering techniques:
                  - NVidia > Dynamic Noise (less perceptible)

                  - ATI/AMD > Dynamic 45/90 degree bars

                  - Intel > Static 90 degree bars (most perceptible)

                  Given my experience with Intel support is better to avoid their hardware the next time. A few years ago I discovered a glitch with Intel Wireless adapters that has continued unfixed in later products, over 100 people confirmed to be having the issue and Intel's immediate response was to discontinue the product's support moving it to legacy and of course never fixing the issue.

                  • 6. Re: Dithering on iGPUs

                    This may help you even if Optimus is enabled: freeware - henteko.co.jp!

                    I've used it on my notebook which has only HD4400.