9 Replies Latest reply: Mar 30, 2012 1:38 AM by andy7panda
cjed Level 1 Level 1
My new mac mini 2010 produces flickering image on my Samsung SyncMaster 206BW monitor (plugged using the provided HDMI to DVI adapter) : it isn't obvious overall, however it especially shows on some dark gray colors. It's like an old CRT monitor with too low refresh rate. It was ok with my previous mac (G4 MDD) on the same monitor, whatever refresh rate (60 and 70Hz).

Snow Leopard only allows 60Hz on the mac mini (should be ok as it isn't CRT), and I'm not confident using 3rd party utilities to try to add 70Hz option (some have experienced stability issues or out of range - that requires rebooting in safe mode).

I plugged the power cord on another plug, and also put the LCD display farther, to check for interference problem, however it didn't help.

Is this a defect with the Nvidia 320M chipset ?


Message was edited by: cjed

Mac Mini 2010, Mac OS X (10.6.4), 2,4 Ghz Core2 Duo ,4 Go ram
  • cjed Level 1 Level 1
    By doing more search, it seems many people are experiencing flickering problem with the mac mini (varies from monitor vendor, Samsung’s are reported to work bad with the mini). A workaround with previous minis (without HDMI) was to connect to the monitor using VGA (through mini DVI to VGA adapter)… Replacing the mac mini/motherboard many times didn’t work for these people, so they are implying the problem comes from Apple’s driver software (and thus could/should be fixed in a later update). Here are a few useful links (among many other) I found :


    http://www.ehmac.ca/mac-ipod-help-troubleshooting/80230-flickering-mac-mini-lcd. html

    The Samsung 206BW doesn’t seem to allow refresh rate above 60hz at 1680×1050, however some have had good result (with other monitors) using 58 or 57hz (using a third party utility).
    I tested lower resolutions through Apple’s monitors preferences pane, and some provide additional refresh rates (70 and/or 75hz) : for most, switching the refresh rate higher didn’t fix the flickering issue. Moreover, the 1024×768 resolution didn’t experience flickering, even at 60hz, while the “1024×768 (stretched)” (in fact both modes display stretched image) did flicker whatever refresh rate !

    Message was edited by: cjed
  • cjed Level 1 Level 1
    As some users had less flickering connecting the monitor through VGA, I bought the Apple mini display port to VGA adapter, and here are the results :
    -the flickering seems gone (at least very slight), particularly on gray tones where the problem was huge.
    -however the image now has a pink tint (on white), and colors (white) are oversaturated (no mean to fix this through ColorSynch settings nor monitor's settings).
    -the text and controls borders are less sharp.

    Then it isn't really usable, and I'm stick with DVI and flickering (that at least mainly occurs on gray colors, hopefully not the most used).

    Will Apple provide soon an update to GeForce 320M chipset driver, as it is likely to be a software problem ?

    Message was edited by: cjed

    Message was edited by: cjed
  • BSteely Level 5 Level 5
    It could very well be that you are just seeing the FRC conversion taking place in the monitor to go from 8-bit video to 6-bit plus 2-bit FRC (the panel is likely 6-bit). You should try finding a real 8-bit display. The problem will likely be gone when connected to one of those.
  • cjed Level 1 Level 1
    Thanks BSteely, you are right about the 206BW doing dithering to achieve 8-bit colors, so it could explain the poor quality in VGA. I would have to check with my projector (also through VGA) whether it is the same.

    About the flickering with HDMI to DVI connection, since the Snow Leopard Graphics update it is still here in GarageBand, however it doesn't show anymore on the gray background of my web site, so it seems rendering has been improved in Safari, really strange (I would expect same behavior in all applications).

    I also checked pluging the monitor to a 2-pin connector (instead of 3-pin), in case of a ground loop (mac mini being 2-pin now). However it didn't help (and I would have - did - go back to 3-pin connection for the monitor whatever result, for safety reason).

    Then I really think it has to do with software (or at least could be fixed through a driver firmware update).

    Message was edited by: cjed

    Message was edited by: cjed

    Message was edited by: cjed
  • BSteely Level 5 Level 5
    About why you may not see flickering on gray in Safari on your website, it could be that particular gray level is one that can be achieved directly by 6-bits. In that case no dithering is taking place. So it may have nothing to do with Safari. It could just be the magnitude of the gray level chosen is not a level requiring 8-bit drive.
  • cjed Level 1 Level 1
    Yes, dithering could explain why it happens on some grays and not on other (some gray colors are known to reveal poor quality of LCD screens, through inversion test), however the flickering appears mostly for dark gray areas.
    Moreover since the graphics update, at least one of the gray colors that experienced the problem doesn't anymore, while others (those grays in GarageBand) still do.
    I then think the digital video output of the mac mini (320M chipset) is less stable than my old dedicated video card (Radeon 9000 Pro), that worked fine on the same monitor in DVI. And the graphics update may have enhanced a little the output stability.
    It may also be a power unit default in the mac mini.

    A monitors compatibility list would be nice for the mac mini, as it seems it has been experiencing compatibility problems for years. A test software from Apple may allow to check for the chipset (in case of an hardware default), as they did for previous Nvidia 8800 in Mbp.
  • cjed Level 1 Level 1
    The 10.6.7 update didn't fix grays flickering.

    Moreover, using Apple's mini display port to DVI adapter (instead od HDMI to DVI adapter) didn't solve the problem either.

    Apple really should work on this, or provide some tools to check hardware (it is the same with stock 2*1 Gb memory, or third-party 2*2Gb, 2*4Gb).

    Message was edited by: cjed
  • Danington Level 1 Level 1

    I have the 2011 Mac Mini server and have the same problem. It's connected to my Dell U2410 and the display flickers as if it were refreshing at 50Hz or something. I've tried connecting via HDMI and Thunderbolt (through to DVI adapter).

    I also have a PC connected to this screen and the display is rock solid... I suspect a driver could resolve this, until then I'll just keep the paracetamol nearby I guess

  • andy7panda Level 1 Level 1

    I have experienced the same problem connecting Samsung SyncMaster B2230 display to a Hackintosh with nVidia GTX 460SE via DVI-DVI cable, some particular shades of gray visibly flicker depending on the horizontal view angle, the lower I bend the better I see it. When I connect the same display to Mac Book Pro 13" – the problem vanishes. I'm on 10.7.3

    Any other ideas or workarounds? I have lost my DVI-to-VGA adapter so I can't try one you have provided in this thread.