fix (hack) for 30" Cinema HD display dancing pixels

I did some more experiments to see the limits of what the monitor can sync on. The following settings will give even a bit more margin than the normal 58Hz george talks about.

Horizontal Vertical
Active 2560 1600
Front Porch 48 1
Sync Width 32 4
Back Porch 48 1

Then set the pixel clock to 252MHz and hit tab. Save the settings, reboot, and make sure you select the 58H refresh rate from your display control panel afterwards.

You can probably go a bit lower on the pixel clock (my monitor goes down to 248MHz before totally losing its mind), but its best to leave some margin.

Also, if you want to slow down just a bit but maintain 60Hz refresh (if for some reason you think it matters), use the above porch settings with a 259MHz pixel clock.

Further indication that the dvi channel is flaking out: When I take my pixel clock up to ~278MHz, I finally get dancing pixels with the image George posted, which gets really bad about 280MHz. Anything slower than that is absolutely fine. Above 282MHz, my monitor refuses to lock.

If you have dancing pixels, check for an updated driver, whichever card you're using. (I have an ATI card. This worked immediately...)

Put the word "sleep" into the search field.

https://support.ati.com/ics/support/default.asp?deptID=894

ATI says: Fixed green pixelation corruption issue after sleep on Apple Cinema HD (DVI). Corruption may occur on a select few X800 XT cards with LCD panels after the system wakes from sleep. The problem primarily affects flat panel displays connected to the card's DVI port. The bug was predominantly reported on the 23" Apple Cinema HD but has also occured on other displays. The update should be (re)applied after other driver and OS updates. Future versions of ATI Driver updates and ATI Displays will include this hotfix.

-------

NOTE: I just bought my 23" Apple Cinema Display last week (mid December '05). Ditto for the Radeon X800 XT card. The driver that came on the ATI CD was still the old one...even though ATI posted the driver update way back in March.

Dual G5 (first model) Mac OS X (10.3.9)

ATI posted an update for the driver. They're calling it a Hotfix.

https://support.ati.com/ics/support/default.asp?deptID=894

To get it, put the word "sleep" into the search field.

ATI says: Fixed green pixelation corruption issue after sleep on Apple Cinema HD (DVI). Corruption may occur on a select few X800 XT cards with LCD panels after the system wakes from sleep. The problem primarily affects flat panel displays connected to the card's DVI port. The bug was predominantly reported on the 23" Apple Cinema HD but has also occured on other displays. The update should be (re)applied after other driver and OS updates. Future versions of ATI Driver updates and ATI Displays will include this hotfix.

Whoops - sis reported an improperply centered screen with those settings. One should probably use a larger back porch value like 64:

H Active: 2560
H Front Porch: 48
H Sync Width: 32
H Back Porch: 64
V Active: 1600
V Front Porch: 1
V Sync Width: 4
V Back Porch: 1

Pixel Clock: 252 MHz
(this will result in a refresh slightly lower than 58Hz, I believe)

Gentlemen and Ladies,

I recently purchased a 30" ACD, ordered a ATI Radeon X800XT card. Once installed, I was happy to see everything working fine until I too became victim of the "dancing pixels" syndrome. This occured approx 30 minutes into turning the monitor on.

I had been researching buying the monitor for quite some time and had followed this thread. So I downloaded SwitchRes X and created a new profile running at 58Hz as the default was set to 59.9Hz.

To my amazement the pixels have not shown their ugly faces again. It has been 5 days of non-stop testing. Zilch.

When I do set the resolution to 2560x1600 at 60Hz they all magically reappear.

Thank you very much Daniel for brining this solution to light. If I had not found this FIX I would have been very disappointed after having spent so much money.

Regards,
Max - One happy 30" ACD owner.

P.S. The monitor is worth every penny 🙂

Ok, here's my story:

Bought a 30" Cinema HD from the Apple store in Houston this past saturday, brought it home, hooked it up to my PM dual 2.7ghz with AGP ATI Radeon 9650 and all seemed fine until I viewed something 'black'. Anything black showed rampant dancing pixels, both red and green at different times. I had been running two 20" Dell 2001FP over DVI for the previous 9 months with no problems. I took the monitor back to the Apple store and with the help of one of the guys there set to the task of trying to isolate the problem.

First we hooked up my 'new' monitor to a new dualcore powermac they had in the store (i'm assuming nvidia 6600 card) and it worked fine.. blacks were solid. Then we hooked up a store 30" monitor to my powermac, again, display was fine. Hooked my 30" back to my powermac, and boom, dancing pixels again. For good measure we tried another power mac (different video card) and another 30" monitor with the same results. Only my monitor and my video card caused the problem.

I managed to get a new 30" and exchange my 6 hour old display. This one seemed to work fine with my powermac in the store. I took it home and seemed fine for a day, but then I was messing with an aquarium screensaver that fades the bakground color between blues and blacks, and during the transitions i could see some dancing pixels. Not as bad as before, but definately there.

I found this thread and tried the switchres X hack, but no dice. Even tried the custom settings from further down in the thread, it seemed to make it a bit better, but still have them.

So in summary, this is my second monitor and the monitor does seem to be involved but I don't think it can be the only factor. I think it must be some weird compatability issue with certain cards and certain monitors over the duallink dvi port. As I said I never had this issue with 2 monitors at 1600x1200.

I'm thinking of taking my whole rig back to the apple store next week and seeing if we can try a different video card. At this point i'm even willing to pony up the cash for an alternative card if it will work.

Does anyone else have other suggestions or possible fixes?

Thanks,

Powermac 2.7ghz dual - ati radeon 9650 - 30" cinema hd Mac OS X (10.4.4)

I believe there are (at least) two problems with these monitors. One is the "dancing green pixels" problem. The other is the flashing red or blue short lines on a black background. The first problem exists in many (most or even all?) of these monitors, but it shows up at a different frequency in different monitors. It typically goes away for a while when the monitor is power cycled. The second problem is less prevalent. It seems to appear more in recent production monitors, and it is more disturbing.

I'm not a flat-panel engineer, but my guess is that both problems are caused by signal integrity issues either in the DVI receiver chips, the circuit boards, or internal connectors in the monitor.

Outstanding Fix!! Thanks for the post. My 30" had all kinds of dancing pixels on the screen especially in my black areas when using Final Cut Pro & After Effects. The SwitchRes 58Hz did the trick!!

What did we ever do before user forums?

Solution:

Change the color options in preferences to, for example, sRGB and of blue pixels go OUT!!!

58hz. It did remove most of the flickering pixels, but some are still there.

I've just downloaded this and set up as described and guess what - no dancing pixels 🙂

I get flickering white pixels around small black areas (say a quicktime window with a black image) when my res is at 58Hz. At fullscreen, it looks fine at 58Hz. A white pixel here and there.

When I switch to 60Hz, the situation is reversed. I DONT see pixels in small black areas of the screen like a quicktime window, but I DO see them in fullscreen - a lot, mostly red pixels, no white pixels.

I downloaded all the latest drivers from the ATI site, I've reset the PRAM. Nothing works.

I have a Radeon 9600 Pro in my PowerMacG4 (specifications on side)

This fix works great on the two 30" Apple Cinema Displays I tried it on. No more problems with dancing pixels after 3 days of testing.

I guess that's finally the solution to the problem.

I will try this, but I want to let folks know that my monitor was created on 11/26 according to AppleCare and still has the issue. I'm running it on a Quad with a 6600 in it.

I called 4 Apple Stores and nobody had heard of the problem (right!) and AppleCare didn't either, sadly.

I'll try this fix and post back.