Monitor flicker question in X Windows

Monitor flicker question in X Windows

Post by Ryan Pa » Sat, 03 Apr 1999 04:00:00



I've got a Matrox Millennium (the original one, OEM PCI, 4MB RAM)
connected to a Mag Innovision 720V2 (17" multisync) monitor.  The
monitor guide says that it can "operate at horizontal frequencies of
30 to 70 KHz and vertical frequencies of 50 to 120Hz."  I am using the
XF86-SVGA server in XFree86 3.3.3.1.  Currently, I am operating at
1024x768 resolution, 32 bpp, 70Hz refresh rate.

My monitor has a lot of occasional flicker.  It's not the same type
flicker as a low refresh rate, but instead large flicker lines which
show up.  This tends to occur when I'm running a large program, but I
can't honestly claim a direct connection.  (If that was the case,
would the problem be due to my PCI bandwidth?  Why don't I have
problems in other operating systems?)

My guess is that it's a horizontal sync problem.  But my monitor guide
says that a standard 1024x768, 70Hz picture has a horizontal sync of
56.5KHz.  This number (56.5KHz) is what is listed in
/etc/X11/XF86Config).  Additionally, the monitor guide says it should
operate at ANY horizontal rate from 30 to 70KHz, not just the
"standard" rates.

Have any of you had similar problems?  Any suggestions on how to fix
it?

Thanks for your help!

Ryan Park

[remove spaces to send e-mail]

 
 
 

Monitor flicker question in X Windows

Post by John Thompso » Sat, 03 Apr 1999 04:00:00



> I've got a Matrox Millennium (the original one, OEM PCI, 4MB RAM)
> connected to a Mag Innovision 720V2 (17" multisync) monitor.  The
> monitor guide says that it can "operate at horizontal frequencies of
> 30 to 70 KHz and vertical frequencies of 50 to 120Hz."  I am using the
> XF86-SVGA server in XFree86 3.3.3.1.  Currently, I am operating at
> 1024x768 resolution, 32 bpp, 70Hz refresh rate.

> My monitor has a lot of occasional flicker.  It's not the same type
> flicker as a low refresh rate, but instead large flicker lines which
> show up.  This tends to occur when I'm running a large program, but I
> can't honestly claim a direct connection.  (If that was the case,
> would the problem be due to my PCI bandwidth?  Why don't I have
> problems in other operating systems?)

> My guess is that it's a horizontal sync problem.  But my monitor guide
> says that a standard 1024x768, 70Hz picture has a horizontal sync of
> 56.5KHz.  This number (56.5KHz) is what is listed in
> /etc/X11/XF86Config).  Additionally, the monitor guide says it should
> operate at ANY horizontal rate from 30 to 70KHz, not just the
> "standard" rates.

> Have any of you had similar problems?  Any suggestions on how to fix
> it?

My monitor did something like that for several months.  Then
one morning it just up 'n' died.  Took it to a fellow that
fixes tese things and he said a transformer went out.  A
used monitor cost less than it would have to fix it so
that's what I did.

--



 
 
 

Monitor flicker question in X Windows

Post by Shashank Misr » Sun, 04 Apr 1999 04:00:00


another possibility is external magnetic interference.

For example, my power strip used to be located between monitor and
computer case. When I added a small inkjet (and the corresponding power
adapter, which contains a transformer), my monitor flickered in the
exact same manner you described. All kinds of things can cause this, but
watch things like power supplies, other things with electron guns
(tv's), large fans.

shashank

 
 
 

Monitor flicker question in X Windows

Post by Ryan Pa » Mon, 05 Apr 1999 05:00:00


On Sat, 03 Apr 1999 16:08:49 -0600, Shashank Misra


>another possibility is external magnetic interference.

>For example, my power strip used to be located between monitor and
>computer case. When I added a small inkjet (and the corresponding power
>adapter, which contains a transformer), my monitor flickered in the
>exact same manner you described. All kinds of things can cause this, but
>watch things like power supplies, other things with electron guns
>(tv's), large fans.

>shashank

Thanks for your help.  You're probably describing the same type of
flicker I'm encountering.  However, this flicker only occurs in X
Windows -- not in Windows 95/98/NT, nor in command-line mode.  Any
other ideas?

Thanks,

Ryan Park

 
 
 

Monitor flicker question in X Windows

Post by David Ript » Thu, 08 Apr 1999 04:00:00




>On Sat, 03 Apr 1999 16:08:49 -0600, Shashank Misra

>>another possibility is external magnetic interference.

>>For example, my power strip used to be located between monitor and
>>computer case. When I added a small inkjet (and the corresponding power
>>adapter, which contains a transformer), my monitor flickered in the
>>exact same manner you described. All kinds of things can cause this, but
>>watch things like power supplies, other things with electron guns
>>(tv's), large fans.
>Thanks for your help.  You're probably describing the same type of
>flicker I'm encountering.  However, this flicker only occurs in X
>Windows -- not in Windows 95/98/NT, nor in command-line mode.  Any
>other ideas?

Go to www.repairfaq.org and start going through the monitor section.
You'll find a lot of info on this kind of problem.  (And everything
else.)

Are you by any chance using different refresh rates in Windows and
Linux console than you are in X?  If so, set your X refresh rate to
match what you use in Windows, and see if that works around the
problem.  (Of course, it would be even nicer to find and fix the
root cause.)

Example:
I have a magnetic field in my ba*t office that causes displays
(2 different monitors, moved all over the room) at 70, 72, 75, and
85 Hz to shake from side to side, but does not affect displays at
60 or 100 Hz.  (60 Hz is the power freqency; your guess is as good
as mine for 100 Hz.)  Shaking continues when I use an unplugged UPS
instead of wall power, so it's definitely a field not "dirty" power
through the cable.  It stops when I cut the house's power at the
breakers, so it's something local.  Next step: turning off one
breaker at a time, to localize the cause.

--

spamgard(tm): To email me, put "geek" in your Subject line.

 
 
 

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