Occassional display flicker in dual-monitor mode

Occassional display flicker in dual-monitor mode
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Mdoc @ 24th Oct 09:30PM:
Occassional display flicker in dual-monitor mode

I have a particular problem:

The problem I'm having is this: In dual-monitor configuration, my one of my displays flickers once every few minutes. When it flickers, the flicker happens only on one or the other monitor, and never both monitors. My Samsung Syncmaster 226bw monitor's native resolution is 1680x1050, and the second monitor (Gateway FPD1500) is 1024x768. There is flickering on one monitor (one or the other monitor at a time), once every few minutes. In the flickering split-second, I see expanded, distorted text on the screen, like the text I was looking at exploded, then returned to normal display. There is otherwise nothing wrong with the display in either monitor. You have to have a fast, trained eye to catch that. Ever come across a problem like that?

I have determined that reduced blanking from my video card is in effect (pixel clock is at 119 MHz at 60 Hz vertical rate). This doesn't resolve anything, anyway, because at 1680x1050, the pixel clock is well below the max of about 165 MHz in standard blanking mode. (If you don't know what I'm on about, don't worry--I know it's a non-issue.)

The flickering seems to stop once the dual-monitor set-up is configured for single monitor display.

A possibility: the power supply is just barely providing enough power to drive the Visiontek X1300 XGE video card when in dual monitor mode. It provides only 300 watts. But it does meet the spec power requirements for the video card. And the card supports dual link DVI-I (two connectors), but both monitors only have single link DVI connectors. A single link DVI supports a max resolution of 1920x1200, which is enough for my dual-monitor set-up.

I downloaded PowerStrip 3.8, but adjusting the Horiz/Vert refresh rates didn't effect the anomaly.

I'm getting a new card, VisionTek HD 4670 with 1GB RAM and a new 400W power supply, Corsair, to replace the standard 300W PS. Both are from TigerDirect.

Right now I'm reading up on video card memory bandwidth ("memory width") and the marketing crap associated with those specs. Not that I think this has anything to do with my problem.

Anybody have any remarks?

System specs

koitsu @ 25th Oct 04:37PM:
Re: Occassional display flicker in dual-monitor mode

said by Mdoc :

... In the flickering split-second, I see expanded, distorted text on the screen, like the text I was looking at exploded, then returned to normal display. There is otherwise nothing wrong with the display in either monitor. You have to have a fast, trained eye to catch that. Ever come across a problem like that?

You must be using LCDs. What you're describing sounds exactly like an LCD monitor attempting to automatically detect/figure out phase, horiz and vert frequency (not refresh rate!), and other parameters. This is often done when the monitor either a) is told to via whatever menu interface it has, b) when changing video modes (e.g. your 1680x1050 screen is told to run at 800x600), c) when the H/V frequencies change on the fly, or d) when the video signal is lost. I'm willing to bet what's happening is either (c) or (d).

Have you tried doing "auto-configuration" on both of your monitors? That is to say, go through the menu interface on your LCDs and pick whatever the "auto-setup" option is? I've seen this fix what you describe on an older Sony LCD I had -- otherwise every so often it'd auto-adjust phase (not sure what was causing that) on its own.

Regarding H/V frequencies for video modes -- all of that is supposed to get worked out between the video card/OS and the monitor via DDC. This applies to both VGA and DVI.

said by Mdoc :

A possibility: the power supply is just barely providing enough power to drive the Visiontek X1300 XGE video card when in dual monitor mode. It provides only 300 watts. But it does meet the spec power requirements for the video card. And the card supports dual link DVI-I (two connectors), but both monitors only have single link DVI connectors. A single link DVI supports a max resolution of 1920x1200, which is enough for my dual-monitor set-up.

I'm doubting this -- if the video card lost power, voltages "went askew", etc. I'd expect your machine to lock up, not one of your two monitors to freak out. My recommendation would be to completely replace the video card -- get a different brand from a different vendor (e.g. don't go with VisionTek and try something like nVidia instead).

said by Mdoc :

I downloaded PowerStrip 3.8, but adjusting the Horiz/Vert refresh rates didn't effect the anomaly.

PowerStrip? People still use that? Does it even work with LCDs? Probably not worth the time to mess with it.

said by Mdoc :

I'm getting a new card, VisionTek HD 4670 with 1GB RAM and a new 400W power supply, Corsair, to replace the standard 300W PS. Both are from TigerDirect.

Right now I'm reading up on video card memory bandwidth ("memory width") and the marketing crap associated with those specs. Not that I think this has anything to do with my problem.

That definitely has nothing to do with your problem. :-)
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.
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Mdoc @ 25th Oct 06:32PM:
Re: Occassional display flicker in dual-monitor mode

said by koitsu :

You must be using LCDs. What you're describing sounds exactly like an LCD monitor attempting to automatically detect/figure out phase, horiz and vert frequency (not refresh rate!), and other parameters. This is often done when the monitor either a) is told to via whatever menu interface it has, b) when changing video modes (e.g. your 1680x1050 screen is told to run at 800x600), c) when the H/V frequencies change on the fly, or d) when the video signal is lost. I'm willing to bet what's happening is either (c) or (d).

(Yes, of course they're LCDs.) Interesting culprit theories. Didn't even think about this. Neither monitor has the auto-configuration menu item.

Regarding DDC, that's new to me. Did a little research. I was trying to see if manual adjustment of H/V freq. with S/W control flushed out any clues about the anomaly. That's why I used PowerStrip. No clue surfaced, just that the H/V thing is cleared as the culprit. Any suggestions regarding the DCC?

Maybe you're right about the PSU not being the culprit, but I'm replacing the old PSU anyway--needs to be done anyway. And I also may just return the VisionTek card and stay with the current card I have. After I swap the cards out and test for this anomaly.

edit: I just won a bid for another Samsung Syncmaster 226bw monitor on ebay to replace the 1024x768 monitor. Maybe the video card just doesn't like the mixed resolutions and having dual monitors of the same resolution will resolve the problem. I'll do that first before anything else.
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Mdoc @ 26th Oct 12:21AM:
Re: Occassional display flicker in dual-monitor mode

Update: After setting the 226bw monitor resolution to 1024x768 (same resolution as the other monitor), the problem still exists. I saw it happen from the corner of my eye in less than an hour after that.
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Mdoc @ 2nd Nov 10:58PM:
Re: Occassional display flicker in dual-monitor mode

The problem is fixed. I bought a used monitor (on ebay) the same size and the same model as my largest monitor, installed it, and there's been no more flickering for hours. They're both the same model: Samsung SyncMaster 226bw, and I'm surprised the price for a new one still hasn't dropped since two years ago when I bought the first one. Real popular monitor and well liked.

Funny thing: the VisionTek X1300 XGE video card didn't like the mixed size dual monitors even when I set the bigger monitor to the same resolution as the smaller one. Still flickered, though not as often.

I've never replaced the video card and didn't have to. I ran into problems with TigerDirect sending me the wrong card-- not once, but twice. I cancelled my order for a refund because I don't need it anymore.

I did replace the power supply with a 400 watter from Corsair, which did not, of course, alleviate the problem. Still glad I did it; it's a better PSU than the 300W Bestec PSU.

Problem solved, thanks for the rather small help. Heh... :)
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