Monitor too old or XF86Config Problems?

[squeegy]

I recently did a hard drive install of Knoppix to my workstation, goodbye Windows XP. But one thing I notice on occasion is a the right side of my screen flickers. It is not constant but it is not infrequent enough to go unnoticed. First I started looking around the forums here and read all the posts about possible EMF interference, but it does not flicker in windows so that does not seem like the cause.

I cannot seem to figure out if the changes that i made to /etc/X11/XF86Config are taking effect or not. I've made some changes to it and i restart my X server and they do not seem to take effect? Does anyone know a way to tell for sure what frequencies X is using?

I have attached a link to my monitor specifications and my XF86Config file (generated by Knoppix). I noticed one thing in particular the Gateway website says H-Sync is 31-69 and V-Sync is 50-160. Does that make the stuff below in bold incorrect? It would seem that 30 down there should be 31. But is VertRefresh the same as Vertical Sync? Also is my ModeLine entry correct?

Section "Monitor"
Identifier "Monitor0"
VendorName "GWY"
ModelName "GWY1b67"
HorizSync 30 - 69 # DDC-probed
VertRefresh 50 - 120 # DDC-probed
# These are the DDC-probed settings reported by your monitor.
# 1024x768, 75.0Hz; hfreq=60.02, vfreq=75.03
ModeLine "1024x768" 78.75 1024 1040 1136 1312 768 769 772 800 +hsync +vsync

Monitor Specifications (http://support.gateway.com/s/MONITOR/7003421/700342102.shtml)

Preset Timings (http://support.gateway.com/s/MONITOR/7003421/700342103.shtml)

Thanks
Michael

[Raoul_Duke]

Yeah, i would change the refresh parameters to match the monitor ones........X doesn't always get it spot on ;)

[squeegy]

Ok then, my next question is in Knoppix when I change XF86Config or XF86Config-4 and Ctrl-Alt-BackSpace it does not SEEM to change any settings. How can I be sure that the settings have taken effect basically.

[EnigmaOne]

Originally posted by squeegy
Ok then, my next question is in Knoppix when I change XF86Config or XF86Config-4 and Ctrl-Alt-BackSpace it does not SEEM to change any settings. How can I be sure that the settings have taken effect basically.

Many monitors have a front panel OSD selection that will display the input frequencies. As I recall, ViewSonic calls it 'ViewMeter' and Samsung terms theirs 'Display Mode'. For your Gateway monitor, simply activating the OSD should display the current operating resolution and V-Sync at the top of the OSD panel.
You can use this as a means of instant feed-back to see if your changes are being implemented or not; and, if you're editing XF86Config exclusively, I'm willing to bet that they aren't.

If you have an XF86Config-4 file, you should be editing *that* file preferentially. On my systems, the XF86Config file goes un-modified, and is exactly the way it was created on installation. I've played all sorts of games with the video and pointing sub-systems, and have confined my changes to the '-4' file.

With that said, I have found that, for certain monitors, I've had to artificially limit the upper range specification for H-Sync or V-Sync to get optimum performance from a particular hardware configuration.
You might be in the same boat.

[squeegy]

I just changed my XF86Config-4 file to the sync rates suggested by gateway, but nothing seems to really have changed as far as I can tell. The little flicker is still there on occasion. and my OSD panel does not display any frequency info, just went through all the menus and everything. Is there any other way to tell that it is actually using XF86Config-4? or that it is actually using the new rates that I just supplied from within X?

EngimaOne you mentioned something about artificially lowering the upper limit on my rates. with that said could you recommend some values that I should try? i am a little unclear by what you mean by that. I changed H: to 31-69 and V: to 50-160, if i'm still noticing the problem should I maybe change the V: back to 50-120 and see if changing 30 to 31 in the H helps?

Hope this all makes sense.

[EnigmaOne]

Originally posted by squeegy
I just changed my XF86Config-4 file to the sync rates suggested by gateway, but nothing seems to really have changed as far as I can tell. The little flicker is still there on occasion. and my OSD panel does not display any frequency info, just went through all the menus and everything. Is there any other way to tell that it is actually using XF86Config-4? or that it is actually using the new rates that I just supplied from within X?

EngimaOne you mentioned something about artificially lowering the upper limit on my rates. with that said could you recommend some values that I should try? i am a little unclear by what you mean by that. I changed H: to 31-69 and V: to 50-160, if i'm still noticing the problem should I maybe change the V: back to 50-120 and see if changing 30 to 31 in the H helps?

Hope this all makes sense.

Interesting that your OSD doesn't have the figures in the top bar. Their screens for that model OSD panel shows them.
Must be a firmware revision at some point in manufacturing.

I leave the horizontal at the manufacturer's full specified range for that specific monitor, and fiddle with Vf (and only to lower it from the vendor's stated max limit) a bit.
I've had to do this to optimize image quality on several types of LCD monitors, and a handful of CRT monitors--to take care of blurring of fine lines and so forth.

While most CRT monitors behave--in general--fine at the optimal-to-higher-end of their performance specs, they usually don't do very well at the top-end of their specs.
XFree86 may be driving your monitor harder than the monitor driver presets in winxp allow for; bringing out some flicker that you might not see otherwise; so......

You might try changing the V-sync to an upper limit of 85Hz (VESA standard) and see if that helps. (V: 50-85)
Then try 75Hz. (IIRC, 75 was spec'ed-out in the preset timing modes for your particular monitor--though I forgot which resolution setting it was for. Guessing it was 1280x1024.)
(V: 50-75)
You could also try 60Hz as an upper Vf limit, but that's pretty hard on my own eyes--even at 1024x768--so I hesitate to recommend it. (V: 50-60)

Without sitting in front of your monitor when this is happening, I'm left to fall-back on previous experience and make some generalized guesses...

A recommendation:
If you have a monitor extension cable attached, get rid of it and run the monitor with the stock cable attached directly to the video card.
Same thing for a KVM, if you're using one.
If you're looping the video through a dxr3 DVD decoder board, then to the monitor...bypass that for the time being and go direct.

A hypothesis:
With what I assume to be a sporadic flickering issue going on, this sounds suspiciously like it *could* actually be related to AC power anomolies or stray magnetic fields. (I've had to deal with similar stuff more than too many times in the past.)

A few questions:
How certain are you that the AC power supplied to the monitor is absolutely clean, and within the range of 105VAC to 125VAC? (If you can, check it through several instances the flickering episodes with a plotting power line monitor or oscilloscope.)
Is there anything on the same circuit that might cause power fluctuations on that branch (fax machines, copiers [particularly Xerox brand], heaters, refrigerators, water coolers, particle accelerators)?
If you are running things from a UPS/power line conditioner/surge suppressor, have you tried substituting a different unit, or removing it altogether to see if this clears up your problem? (When such things are on the way out, they can behave in a very weird manner, leaving you to chase the symptoms up blind alleys.)
Speakers, sub-woofers, phones, bulk tape erasers, anything that might possess or generate a magnetic field...have anything like that within several feet of the monitor in question? (Even something as innocent as a heater cord or sub-woofer cables, running past the monitor, can give you fits.)

The reason I ask is, if you made a one-way change from winxp, something might now be different in the physical or electrical environment of the monitor; which you are only now seeing.
If you're dual-booting 'nux/xp, then the above issues may be moot--but not always....
It's all a guessing-game from afar. ;)

[squeegy]

Just in case anyone runs into this problem again, and happens to search and finds this thread, I thought I'd post my solution.

Simply I had to comment out the ModeLine, not exactly sure why this helped or how it would have affected it in the first place. But I did not find these ModeLine's in all the Sample XF86Config's that I looked at.

[EnigmaOne]

Now, that's follow-up!

Thanks for closing the loop, Squeegy.