Samsung SyncMaster 204B blackouts in DVI mode

[WakeFossil]

Dear nVidia drivers experts!

My graphics adater: Asus EN7600GS Top Silent (nVidia Geforce 7600GS)
My monitor: Samsung SyncMaster 204B
Linux driver: 1.0-9742 (tried 9629 and 9631 before: same result)
Windows driver: 93.81

Problem description:
If I'm running my monitor in DVI mode at 1600x1200 (as recommended), then after approximately an hour the monitor goes black for half a second preceded by pixel "snow" (white or green pixels in dark areas). The blackouts get more frequent with time.
In analog mode the problem doesn't occur, but running a TFT in analog mode is IMHO no satisfactory solution.
Other users have encountered this problem as well: http://www.prad.de/board/thread.php?threadid=27604 (german TFT forum)
The problem occurs under Windows and Linux.

I'm sure that this is a monitor problem and my domestic Samsung rep has told me to send in the monitor for inspection, but I would appreciate it if I could find a workaround and don't have to send in my monitor.
So here comes my question: Are there any driver settings I could try to avoid the blackouts?
In the thread mentioned above a rather weird workaround has been suggested: to change the refresh rate to 58 Hz. I tried this, but it didn't help. (I don't think the refresh rate is of any significance in DVI mode.)
Another hint given in the thread mentioned above says that the problem didn't occur if a second monitor was attached (no matter if analog or with DVI).
Can I fake a dual monitor setup even if I don't have a second monitor? If yes, how?

Any help is appreciated.
Merry Christmas
Andy

P.S.: I am posting this to the ForceWare Drivers forum and to the NVIDIA Linux Forum in order to reach Linux and Windows drivers experts. I hope this isn't regarded as illegal cross-posting.

[WakeFossil]

Some other user using the same monitor with a 7600 GT has told me that he got his monitor replaced and the exact same problem occurred with the new monitor, too. Considering this, I will refrain from getting my monitor replaced as this will not solve my problem.
So this seems to be a general incompatibility issue between nVidia GPUs and the SyncMaster 204B.
Given this finding I and several other users struggling with the combination nVidia / Samsung SyncMaster 204B would highly appreciate a solution / workaround.

Best regards,
Andy

[cestuila]

I am using this monitor on a 8800gtx.(dvi)
Try to decrease luminosity and contrast (with monitor's buttons), it work for me.
At the beginning i had many blackouts on both windows and linux, actually
1 or 2 a week .

[WakeFossil]

I just tried this: Reduced brightness and contrast to 0, but the blackouts still persisted.
Any driver settings I could try?

[tha_Bass]

I’m also experiencing blackouts (windows, no linux installed yet). I’ve bought two monitors (syncmaster 204B) and use a MSI NX7950GT (NVidia) to get a dual monitor setup.
I have the same problem on both of my monitors, although one of them happens to break down (blackout) more often than the other one.
I would like to stay informed about driver updates / workarounds / solutions.
Also the problem does only occur in DVI-mode.

cheers,

Bas

[gbugher]

I had the same issue with my 204B and an 8800 GTS.

The problem is a defect in the 204Bs made in China. It's commonly known (i.e. basically every 204B owner with a new, high-end card hits it), though Samsung tech support either refuses to acknowledge it or somehow remains ignorant of it (they were wholly useless to me on the phone and just wanted to swap my 204B for another one... which I'd already done.) The 204B can't handle the full 165 MHz transfer rate of DVI, and 1600x1200x24-bit gets perilously close to it.

You can fix the issue as follows:

nVidia Control Panel -> Display -> Manage Custom Timings -> Create or Edit (depending on if you have one for 1600x1200 at 60Hz or not) -> Advanced -> switch the timing standard to "CVT Reduced Blank"

Once I set the timing to CVT Reduced Blank (which drops your refresh rate from 60.00 Hz to 59.92 Hz), the blackouts and pixel snow went away completely.

[WakeFossil]

Thanks a lot, gbugher!

That solved the problem (at least under Windows).
Now I'm trying to get this to work under Linux, too.
I'll let you know if I succeeded.

[tha_Bass]

Thanks a lot!!
This seems to work :-)
I'm also interested how to make it work using linux.

cheers,

Bas

[WakeFossil]

This is how you edit your xorg.conf to activate reduced blanking:

1) Generate the appropriate Modeline:
$ cvt 1600 1200 60 -r
This creates the following output (well not exactly, I edited the comment and the mode name):
# 1600x1200 59.92 Hz (CVT 1.92M3-R) hsync: 74.01 kHz; pclk: 130.25 MHz
ModeLine "1600x1200_59.92_rb" 130.25 1600 1648 1680 1760 1200 1203 1207 1235 +hsync -vsync
Add these two lines in /etc/X11/xorg.conf in Section "Monitor".

In Section "Screen" add to each mode list "1600x1200_59.92_rb" as first entry.

In Section "Device" add this line:
Option "ExactModeTimingsDVI" "yes"
This forces the driver to use the exact mode line and not the closest setting retrieved from EDID (I had quite a hard time figuring that out.)

How to check if Reduced Blanking was activated (apart from the absence of blackouts :-) ) :
Monitor info in the OSD shows a line frequency of 74.1 kHz. (Without Reduced Blanking: 74.9)

Thanks a lot to users pe1chl and kulick from whose postings I got this wisdom.

Enjoy!
Andy a.k.a. WakeFossil

[greg02]

Thanks to WakeFossil & all others who posted the solution to this problem.

I wasted days attempting to troubleshoot this problem first with a Matrox P650 dual-DVI and then an whole slew of Nvidia cards. I replaced the motherboard, memory, DVI cables, and finally one of my two monitors via Samsung's warranty exchange program. Strangely enough, this problem does not manifest when running a GeForce 6800XT dual-DVI, but when i went to a 7600GS the problem returned. It was only after finding this thread that i was finally able to solve the problem.

Samsung should be for this - i spent hours on the phone with their techs & even spoke to an "engineer" and they claimed never to have heard of this problem before. I finally ended up sending the monitor in for exchange, at which time they told me they didn't have any more of this model to exchange with so I would have to either get my (defective?) monitor shipped back to me, or opt for a refund. To make a long story short, it took Samsung over 3 months to get my refund check to me after 10+ phone calls with each rep claiming the check had just been mailed and to call back after 14 business days.

It is not surprising that they don't acknowledge the problem , but between this and the terrible warranty service I received I will *never* buy another Samsung product again. I hope this is useful information for anyone considering returning/exchanging their monitor to Samsung under warranty.

Thanks again to all who contributed to this thread

[SIDDIBE]

Hi all,

Have also bought 2 SAMSUNG SyncMasters 204B. Just used one for a month with VGA input. No problem with this monitor. Just bought a new MSI NX7900GS card to use both monitors with DVI. From the first moment the unused monitor began to flicker on an irregular interval. Changed the DVI connectors of both monitors. Same problem persist with the same monitor. Other one worked fine.
Both monitors are made in SLOVAKIA. The serial number differs only 3 units.

Dirk
Eeklo Belgium

[WakeFossil]

Hi Dirk,

You are lucky that one of your two monitors is working according to spec.
Other people only have 1 out of 4 working...
However: No problemo.
The workarounds have been posted above. The workaround for Windows is in gbugher's posting and the workaround for Linux is in my previous posting.

Andy a.k.a. Wake Fossil