# Warning sign: refresh/rasterbeam issues?
**URL:** https://psychtoolbox.discourse.group/t/warning-sign-refresh-rasterbeam-issues/1769
**Category:** Uncategorized
**Created:** [February 21, 2007, 2:37pm UTC](https://psychtoolbox.discourse.group/t/warning-sign-refresh-rasterbeam-issues/1769 "2007-02-21T14:37:25Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)
#### Post date: [February 21, 2007, 2:37pm UTC](https://psychtoolbox.discourse.group/t/warning-sign-refresh-rasterbeam-issues/1769/1 "2007-02-21T14:37:25Z")
Hi,
I have a script in which I'm trying to present a couple of moving
circles. At the beginning of every trial I see a giant caution sign
that flashes. This appears even if I set a break point prior to my
trial loops, and it seems to be a function of the initial screen
loading. The code I'm using to do this is: [a, rect] =
Screen('OpenWindow', screenNumber, 255,[], 32, doublebuffer+1), where
screenNumber =0, and doublebuffer = 1.
This may to be due to some sort of function of the discrepancy between
the monitor refresh interval from beamposition (whose values can range
from ~9 to ~13 on any given trial), and the monitor refresh interval
from VBLsync and the operating system, both of which are ~16.677.
An example of the output I get when I run my script with this problem
(for 5 trials) is 5 repetitions of this, with slightly differing
beamposition values each time:
PTB-INFO: Using GLEW version 1.3.5 for automatic detection of OpenGL
extensions...
PTB-INFO: This is the OpenGL-Psychtoolbox version 3.0.8. Type
'PsychtoolboxVersion' for more detailed version information.
PTB-INFO: Psychtoolbox is licensed to you under terms of the GNU
General Public License (GPL). See file 'License.txt' in the
PTB-INFO: Psychtoolbox root folder for a copy of the GPL license.
OpenGL-Extensions are: GL\_ARB\_multitexture GL\_EXT\_texture\_env\_add
GL\_EXT\_compiled\_vertex\_array GL\_S3\_s3tc GL\_ARB\_depth\_texture
GL\_ARB\_fragment\_program GL\_ARB\_fragment\_program\_shadow
GL\_ARB\_fragment\_shader GL\_ARB\_multisample GL\_ARB\_occlusion\_query
GL\_ARB\_point\_parameters GL\_ARB\_point\_sprite GL\_ARB\_shader\_objects
GL\_ARB\_shading\_language\_100 GL\_ARB\_shadow GL\_ARB\_shadow\_ambient
GL\_ARB\_texture\_border\_clamp GL\_ARB\_texture\_compression
GL\_ARB\_texture\_cube\_map GL\_ARB\_texture\_env\_add
GL\_ARB\_texture\_env\_combine GL\_ARB\_texture\_env\_crossbar
GL\_ARB\_texture\_env\_dot3 GL\_ARB\_texture\_mirrored\_repeat
GL\_ARB\_transpose\_matrix GL\_ARB\_vertex\_blend
GL\_ARB\_vertex\_buffer\_object GL\_ARB\_vertex\_program GL\_ARB\_vertex\_shader
GL\_ARB\_window\_pos GL\_ARB\_draw\_buffers GL\_ATI\_draw\_buffers
GL\_ATI\_element\_array GL\_ATI\_envmap\_bumpmap GL\_ATI\_fragment\_shader
GL\_ATI\_map\_object\_buffer GL\_ATI\_separate\_stencil
GL\_ATI\_texture\_compression\_3dc GL\_ATI\_texture\_env\_combine3
GL\_ATI\_texture\_float GL\_ATI\_texture\_mirror\_once
GL\_ATI\_vertex\_array\_object GL\_ATI\_vertex\_attrib\_array\_object
GL\_ATI\_vertex\_streams GL\_ATIX\_texture\_env\_combine3
GL\_ATIX\_texture\_env\_route GL\_ATIX\_vertex\_shader\_output\_point\_size
GL\_EXT\_abgr GL\_EXT\_bgra GL\_EXT\_blend\_color GL\_EXT\_blend\_func\_separate
GL\_EXT\_blend\_minmax GL\_EXT\_blend\_subtract GL\_EXT\_clip\_volume\_hint
GL\_EXT\_draw\_range\_elements GL\_EXT\_fog\_coord GL\_EXT\_framebuffer\_object
GL\_EXT\_multi\_draw\_arrays GL\_EXT\_packed\_pixels GL\_EXT\_point\_parameters
GL\_EXT\_rescale\_normal GL\_EXT\_secondary\_color
GL\_EXT\_separate\_specular\_color GL\_EXT\_shadow\_funcs GL\_EXT\_stencil\_wrap
GL\_EXT\_texgen\_reflection GL\_EXT\_texture3D
GL\_EXT\_texture\_compression\_s3tc GL\_EXT\_texture\_cube\_map
GL\_EXT\_texture\_edge\_clamp GL\_EXT\_texture\_env\_combine
GL\_EXT\_texture\_env\_dot3 GL\_EXT\_texture\_filter\_anisotropic
GL\_EXT\_texture\_lod\_bias GL\_EXT\_texture\_mirror\_clamp
GL\_EXT\_texture\_object GL\_EXT\_texture\_rectangle GL\_EXT\_vertex\_array
GL\_EXT\_vertex\_shader GL\_HP\_occlusion\_test GL\_NV\_blend\_square
GL\_NV\_occlusion\_query GL\_NV\_texgen\_reflection GL\_SGI\_color\_matrix
GL\_SGIS\_generate\_mipmap GL\_SGIS\_multitexture
GL\_SGIS\_texture\_border\_clamp GL\_SGIS\_texture\_edge\_clamp
GL\_SGIS\_texture\_lod GL\_SUN\_multi\_draw\_arrays GL\_WIN\_swap\_hint
WGL\_EXT\_extensions\_string WGL\_EXT\_swap\_control
PTB-INFO: OpenGL-Renderer is ATI Technologies Inc. :: ATI Mobility
Radeon X1400 x86/SSE2 :: 2.0.5529 WinXP Release
PTB-Info: VBL startline = 1050 , VBL Endline = 2088805435
PTB-Info: Measured monitor refresh interval from beamposition =
9.907484 ms [100.933797 Hz].
PTB-Info: Will use beamposition query for accurate Flip time stamping.
PTB-Info: Measured monitor refresh interval from VBLsync = 16.738390
ms [59.742903 Hz]. (50 valid samples taken, stddev=0.031696 ms.)
PTB-Info: Reported monitor refresh interval from operating system =
16.666667 ms [60.000000 Hz].
PTB-Info: Small deviations between reported values are normal and no
reason to worry.
PTB-INFO: Using OpenGL GL\_TEXTURE\_RECTANGLE\_EXT extension for
efficient high-performance texture mapping...
WARNING: Mismatch between measured monitor refresh intervals! This
indicates problems with rasterbeam position queries.
----- ! PTB - WARNING: SYNCHRONIZATION TROUBLE ! ----
One or more internal checks (see Warnings above) indicate that
queries of rasterbeam position are not properly working for your setup.
Psychtoolbox will work around this by using a different timing algorithm,
but it will cause Screen('Flip') to report less accurate/robust timestamps
for stimulus timing.
Read 'help BeampositionQueries' for more info and troubleshooting tips.
The current version of Psychtoolbox that I'm using is:
3.0.8 - Flavor: stable - Corresponds to SVN Revision 640
For more info visit:
[http://svn.berlios.de/wsvn/osxptb/?rev=640&sc=0.](http://svn.berlios.de/wsvn/osxptb/?rev=640&sc=0.)
I have also tried the beta version with SVN Revisions up to ( I think
it was) 670 (the latest as of 2 days ago) with the same error. Using
these same versions of Psychtoolbox on a colleague's computer my
script runs fine.
My system specs are: Dell Inspiron I6400 Genuine Intel (R) CPU T2500 @
2.00GHz 2.00 GB of RAM, Windows XP Version 2002. My refresh rate is
set to 60Hz, and my monitor is set to 1.(Multiple Monitors) on ATI
Mobility Radeon X1400 with a resolution of 1680x1050.
I was wondering how to eliminate this warning sign, and also if this
is indicative of deeper issues with respect to timing that I should be
concerned about.
Thank you very much for your help.
Sarah Donohue
Duke University
---
### Author:  [@mariokleiner](https://psychtoolbox.discourse.group/u/mariokleiner)
#### Post date: [February 21, 2007, 11:38pm UTC](https://psychtoolbox.discourse.group/t/warning-sign-refresh-rasterbeam-issues/1769/2 "2007-02-21T23:38:45Z")
The returned beamposition values (VBL Endline) are completely bogus and strongly
indicate a driver bug in the ATI display driver. Either its a bug wrt. dual-display
configurations or a general bug.
Read "help Beampositionqueries" first.
Update to the latest available graphics driver from ATI for your Laptop. One of the big
problems of Laptops under Windows is that many vendors are pretty bad at providing
timely driver updates, something that Apple does much better.
Try the following, restarting Matlab after each change in display settings:
What happens in single-display mode? If you switch assignment of primary and secondary
display? If you only output to the external display? At lower display resolutions? If you set
resolution of the internal and external screen to identical values?
How does PerceptualVBLSyncTest(0) behave? Does it draw yellow horizontal lines, and
where are they located? What are typical values for the VBL Endline when PTB start up?
When PTB detects such trouble it falls back to a simpler timestamping code, so it doesn't
introduce artifacts, but the timestamps are less robust and accurate (but still as good as
the ones in old PTB 2 or in other toolkits). If none of the above gives an improvements, i'll
tell you how to disable the light-show at least and you'll have to live with slightly less
accurate and robust timestamps.
-mario
> --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "donohuesarah" \ wrote:
> \>
> \> Hi,
> \> I have a script in which I'm trying to present a couple of moving
> \> circles. At the beginning of every trial I see a giant caution sign
> \> that flashes. This appears even if I set a break point prior to my
> \> trial loops, and it seems to be a function of the initial screen
> \> loading. The code I'm using to do this is: [a, rect] =
> \> Screen('OpenWindow', screenNumber, 255,[], 32, doublebuffer+1), where
> \> screenNumber =0, and doublebuffer = 1.
> \>
> \> This may to be due to some sort of function of the discrepancy between
> \> the monitor refresh interval from beamposition (whose values can range
> \> from ~9 to ~13 on any given trial), and the monitor refresh interval
> \> from VBLsync and the operating system, both of which are ~16.677.
> \>
> \> An example of the output I get when I run my script with this problem
> \> (for 5 trials) is 5 repetitions of this, with slightly differing
> \> beamposition values each time:
> \> PTB-INFO: Using GLEW version 1.3.5 for automatic detection of OpenGL
> \> extensions...
> \> PTB-INFO: This is the OpenGL-Psychtoolbox version 3.0.8. Type
> \> 'PsychtoolboxVersion' for more detailed version information.
> \> PTB-INFO: Psychtoolbox is licensed to you under terms of the GNU
> \> General Public License (GPL). See file 'License.txt' in the
> \> PTB-INFO: Psychtoolbox root folder for a copy of the GPL license.
> \>
> \> OpenGL-Extensions are: GL\_ARB\_multitexture GL\_EXT\_texture\_env\_add
> \> GL\_EXT\_compiled\_vertex\_array GL\_S3\_s3tc GL\_ARB\_depth\_texture
> \> GL\_ARB\_fragment\_program GL\_ARB\_fragment\_program\_shadow
> \> GL\_ARB\_fragment\_shader GL\_ARB\_multisample GL\_ARB\_occlusion\_query
> \> GL\_ARB\_point\_parameters GL\_ARB\_point\_sprite GL\_ARB\_shader\_objects
> \> GL\_ARB\_shading\_language\_100 GL\_ARB\_shadow GL\_ARB\_shadow\_ambient
> \> GL\_ARB\_texture\_border\_clamp GL\_ARB\_texture\_compression
> \> GL\_ARB\_texture\_cube\_map GL\_ARB\_texture\_env\_add
> \> GL\_ARB\_texture\_env\_combine GL\_ARB\_texture\_env\_crossbar
> \> GL\_ARB\_texture\_env\_dot3 GL\_ARB\_texture\_mirrored\_repeat
> \> GL\_ARB\_transpose\_matrix GL\_ARB\_vertex\_blend
> \> GL\_ARB\_vertex\_buffer\_object GL\_ARB\_vertex\_program GL\_ARB\_vertex\_shader
> \> GL\_ARB\_window\_pos GL\_ARB\_draw\_buffers GL\_ATI\_draw\_buffers
> \> GL\_ATI\_element\_array GL\_ATI\_envmap\_bumpmap GL\_ATI\_fragment\_shader
> \> GL\_ATI\_map\_object\_buffer GL\_ATI\_separate\_stencil
> \> GL\_ATI\_texture\_compression\_3dc GL\_ATI\_texture\_env\_combine3
> \> GL\_ATI\_texture\_float GL\_ATI\_texture\_mirror\_once
> \> GL\_ATI\_vertex\_array\_object GL\_ATI\_vertex\_attrib\_array\_object
> \> GL\_ATI\_vertex\_streams GL\_ATIX\_texture\_env\_combine3
> \> GL\_ATIX\_texture\_env\_route GL\_ATIX\_vertex\_shader\_output\_point\_size
> \> GL\_EXT\_abgr GL\_EXT\_bgra GL\_EXT\_blend\_color GL\_EXT\_blend\_func\_separate
> \> GL\_EXT\_blend\_minmax GL\_EXT\_blend\_subtract GL\_EXT\_clip\_volume\_hint
> \> GL\_EXT\_draw\_range\_elements GL\_EXT\_fog\_coord GL\_EXT\_framebuffer\_object
> \> GL\_EXT\_multi\_draw\_arrays GL\_EXT\_packed\_pixels GL\_EXT\_point\_parameters
> \> GL\_EXT\_rescale\_normal GL\_EXT\_secondary\_color
> \> GL\_EXT\_separate\_specular\_color GL\_EXT\_shadow\_funcs GL\_EXT\_stencil\_wrap
> \> GL\_EXT\_texgen\_reflection GL\_EXT\_texture3D
> \> GL\_EXT\_texture\_compression\_s3tc GL\_EXT\_texture\_cube\_map
> \> GL\_EXT\_texture\_edge\_clamp GL\_EXT\_texture\_env\_combine
> \> GL\_EXT\_texture\_env\_dot3 GL\_EXT\_texture\_filter\_anisotropic
> \> GL\_EXT\_texture\_lod\_bias GL\_EXT\_texture\_mirror\_clamp
> \> GL\_EXT\_texture\_object GL\_EXT\_texture\_rectangle GL\_EXT\_vertex\_array
> \> GL\_EXT\_vertex\_shader GL\_HP\_occlusion\_test GL\_NV\_blend\_square
> \> GL\_NV\_occlusion\_query GL\_NV\_texgen\_reflection GL\_SGI\_color\_matrix
> \> GL\_SGIS\_generate\_mipmap GL\_SGIS\_multitexture
> \> GL\_SGIS\_texture\_border\_clamp GL\_SGIS\_texture\_edge\_clamp
> \> GL\_SGIS\_texture\_lod GL\_SUN\_multi\_draw\_arrays GL\_WIN\_swap\_hint
> \> WGL\_EXT\_extensions\_string WGL\_EXT\_swap\_control
> \>
> \> PTB-INFO: OpenGL-Renderer is ATI Technologies Inc. :: ATI Mobility
> \> Radeon X1400 x86/SSE2 :: 2.0.5529 WinXP Release
> \> PTB-Info: VBL startline = 1050 , VBL Endline = 2088805435
> \> PTB-Info: Measured monitor refresh interval from beamposition =
> \> 9.907484 ms [100.933797 Hz].
> \> PTB-Info: Will use beamposition query for accurate Flip time stamping.
> \> PTB-Info: Measured monitor refresh interval from VBLsync = 16.738390
> \> ms [59.742903 Hz]. (50 valid samples taken, stddev=0.031696 ms.)
> \> PTB-Info: Reported monitor refresh interval from operating system =
> \> 16.666667 ms [60.000000 Hz].
> \> PTB-Info: Small deviations between reported values are normal and no
> \> reason to worry.
> \> PTB-INFO: Using OpenGL GL\_TEXTURE\_RECTANGLE\_EXT extension for
> \> efficient high-performance texture mapping...
> \>
> \> WARNING: Mismatch between measured monitor refresh intervals! This
> \> indicates problems with rasterbeam position queries.
> \>
> \>
> \> ----- ! PTB - WARNING: SYNCHRONIZATION TROUBLE ! ----
> \>
> \> One or more internal checks (see Warnings above) indicate that
> \> queries of rasterbeam position are not properly working for your setup.
> \>
> \> Psychtoolbox will work around this by using a different timing algorithm,
> \> but it will cause Screen('Flip') to report less accurate/robust timestamps
> \> for stimulus timing.
> \> Read 'help BeampositionQueries' for more info and troubleshooting tips.
> \>
> \>
> \> The current version of Psychtoolbox that I'm using is:
> \> 3.0.8 - Flavor: stable - Corresponds to SVN Revision 640
> \> For more info visit:
> \> [http://svn.berlios.de/wsvn/osxptb/?rev=640&sc=0.](http://svn.berlios.de/wsvn/osxptb/?rev=640&sc=0.)
> \>
> \> I have also tried the beta version with SVN Revisions up to ( I think
> \> it was) 670 (the latest as of 2 days ago) with the same error. Using
> \> these same versions of Psychtoolbox on a colleague's computer my
> \> script runs fine.
> \>
> \> My system specs are: Dell Inspiron I6400 Genuine Intel (R) CPU T2500 @
> \> 2.00GHz 2.00 GB of RAM, Windows XP Version 2002. My refresh rate is
> \> set to 60Hz, and my monitor is set to 1.(Multiple Monitors) on ATI
> \> Mobility Radeon X1400 with a resolution of 1680x1050.
> \>
> \> I was wondering how to eliminate this warning sign, and also if this
> \> is indicative of deeper issues with respect to timing that I should be
> \> concerned about.
> \>
> \> Thank you very much for your help.
> \>
> \> Sarah Donohue
> \> Duke University
> \>
---
### Author:  [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)
#### Post date: [February 23, 2007, 4:04pm UTC](https://psychtoolbox.discourse.group/t/warning-sign-refresh-rasterbeam-issues/1769/3 "2007-02-23T16:04:37Z")
Hi Mario,
Thanks for the info! I've tried all of your suggestions including
updating the driver, and I still get the flashing warning sign,
regardless of what I do. When I ran the PerceptualVBLSyncTest(0) I get
yellow lines. One goes across the screen just above the center, and
then the grey square is surround by a black border that has yellow
lines that are located at the top and center that appear to be
occluded by the grey square. The square also isn't uniform, and there
appears to be a triangle that is either a different color or flashing
at a different frequency in the top right corner. The VBL Endline
values seem to always be: 2088805435.
Do you have any other suggestions, or am I at the point where I should
just turn off the warning sign (and how do I do that?), and how off
will this make the time stamps?
Thanks for your help.
Sarah Donohue
--- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "Mario Kleiner"
\ wrote:
> \>
> \> The returned beamposition values (VBL Endline) are completely bogus
and strongly
> \> indicate a driver bug in the ATI display driver. Either its a bug
wrt. dual-display
> \> configurations or a general bug.
> \>
> \> Read "help Beampositionqueries" first.
> \>
> \> Update to the latest available graphics driver from ATI for your
Laptop. One of the big
> \> problems of Laptops under Windows is that many vendors are pretty
bad at providing
> \> timely driver updates, something that Apple does much better.
> \>
> \> Try the following, restarting Matlab after each change in display
settings:
> \>
> \> What happens in single-display mode? If you switch assignment of
primary and secondary
> \> display? If you only output to the external display? At lower
display resolutions? If you set
> \> resolution of the internal and external screen to identical values?
> \>
> \> How does PerceptualVBLSyncTest(0) behave? Does it draw yellow
horizontal lines, and
> \> where are they located? What are typical values for the VBL Endline
when PTB start up?
> \>
> \> When PTB detects such trouble it falls back to a simpler
timestamping code, so it doesn't
> \> introduce artifacts, but the timestamps are less robust and accurate
(but still as good as
> \> the ones in old PTB 2 or in other toolkits). If none of the above
gives an improvements, i'll
> \> tell you how to disable the light-show at least and you'll have to
live with slightly less
> \> accurate and robust timestamps.
> \>
> \> -mario
> \>
> \> --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "donohuesarah" \
wrote:
> \> \>
> \> \> Hi,
> \> \> I have a script in which I'm trying to present a couple of moving
> \> \> circles. At the beginning of every trial I see a giant caution sign
> \> \> that flashes. This appears even if I set a break point prior to my
> \> \> trial loops, and it seems to be a function of the initial screen
> \> \> loading. The code I'm using to do this is: [a, rect] =
> \> \> Screen('OpenWindow', screenNumber, 255,[], 32, doublebuffer+1), where
> \> \> screenNumber =0, and doublebuffer = 1.
> \> \>
> \> \> This may to be due to some sort of function of the discrepancy between
> \> \> the monitor refresh interval from beamposition (whose values can range
> \> \> from ~9 to ~13 on any given trial), and the monitor refresh interval
> \> \> from VBLsync and the operating system, both of which are ~16.677.
> \> \>
> \> \> An example of the output I get when I run my script with this problem
> \> \> (for 5 trials) is 5 repetitions of this, with slightly differing
> \> \> beamposition values each time:
> \> \> PTB-INFO: Using GLEW version 1.3.5 for automatic detection of OpenGL
> \> \> extensions...
> \> \> PTB-INFO: This is the OpenGL-Psychtoolbox version 3.0.8. Type
> \> \> 'PsychtoolboxVersion' for more detailed version information.
> \> \> PTB-INFO: Psychtoolbox is licensed to you under terms of the GNU
> \> \> General Public License (GPL). See file 'License.txt' in the
> \> \> PTB-INFO: Psychtoolbox root folder for a copy of the GPL license.
> \> \>
> \> \> OpenGL-Extensions are: GL\_ARB\_multitexture GL\_EXT\_texture\_env\_add
> \> \> GL\_EXT\_compiled\_vertex\_array GL\_S3\_s3tc GL\_ARB\_depth\_texture
> \> \> GL\_ARB\_fragment\_program GL\_ARB\_fragment\_program\_shadow
> \> \> GL\_ARB\_fragment\_shader GL\_ARB\_multisample GL\_ARB\_occlusion\_query
> \> \> GL\_ARB\_point\_parameters GL\_ARB\_point\_sprite GL\_ARB\_shader\_objects
> \> \> GL\_ARB\_shading\_language\_100 GL\_ARB\_shadow GL\_ARB\_shadow\_ambient
> \> \> GL\_ARB\_texture\_border\_clamp GL\_ARB\_texture\_compression
> \> \> GL\_ARB\_texture\_cube\_map GL\_ARB\_texture\_env\_add
> \> \> GL\_ARB\_texture\_env\_combine GL\_ARB\_texture\_env\_crossbar
> \> \> GL\_ARB\_texture\_env\_dot3 GL\_ARB\_texture\_mirrored\_repeat
> \> \> GL\_ARB\_transpose\_matrix GL\_ARB\_vertex\_blend
> \> \> GL\_ARB\_vertex\_buffer\_object GL\_ARB\_vertex\_program GL\_ARB\_vertex\_shader
> \> \> GL\_ARB\_window\_pos GL\_ARB\_draw\_buffers GL\_ATI\_draw\_buffers
> \> \> GL\_ATI\_element\_array GL\_ATI\_envmap\_bumpmap GL\_ATI\_fragment\_shader
> \> \> GL\_ATI\_map\_object\_buffer GL\_ATI\_separate\_stencil
> \> \> GL\_ATI\_texture\_compression\_3dc GL\_ATI\_texture\_env\_combine3
> \> \> GL\_ATI\_texture\_float GL\_ATI\_texture\_mirror\_once
> \> \> GL\_ATI\_vertex\_array\_object GL\_ATI\_vertex\_attrib\_array\_object
> \> \> GL\_ATI\_vertex\_streams GL\_ATIX\_texture\_env\_combine3
> \> \> GL\_ATIX\_texture\_env\_route GL\_ATIX\_vertex\_shader\_output\_point\_size
> \> \> GL\_EXT\_abgr GL\_EXT\_bgra GL\_EXT\_blend\_color GL\_EXT\_blend\_func\_separate
> \> \> GL\_EXT\_blend\_minmax GL\_EXT\_blend\_subtract GL\_EXT\_clip\_volume\_hint
> \> \> GL\_EXT\_draw\_range\_elements GL\_EXT\_fog\_coord GL\_EXT\_framebuffer\_object
> \> \> GL\_EXT\_multi\_draw\_arrays GL\_EXT\_packed\_pixels GL\_EXT\_point\_parameters
> \> \> GL\_EXT\_rescale\_normal GL\_EXT\_secondary\_color
> \> \> GL\_EXT\_separate\_specular\_color GL\_EXT\_shadow\_funcs GL\_EXT\_stencil\_wrap
> \> \> GL\_EXT\_texgen\_reflection GL\_EXT\_texture3D
> \> \> GL\_EXT\_texture\_compression\_s3tc GL\_EXT\_texture\_cube\_map
> \> \> GL\_EXT\_texture\_edge\_clamp GL\_EXT\_texture\_env\_combine
> \> \> GL\_EXT\_texture\_env\_dot3 GL\_EXT\_texture\_filter\_anisotropic
> \> \> GL\_EXT\_texture\_lod\_bias GL\_EXT\_texture\_mirror\_clamp
> \> \> GL\_EXT\_texture\_object GL\_EXT\_texture\_rectangle GL\_EXT\_vertex\_array
> \> \> GL\_EXT\_vertex\_shader GL\_HP\_occlusion\_test GL\_NV\_blend\_square
> \> \> GL\_NV\_occlusion\_query GL\_NV\_texgen\_reflection GL\_SGI\_color\_matrix
> \> \> GL\_SGIS\_generate\_mipmap GL\_SGIS\_multitexture
> \> \> GL\_SGIS\_texture\_border\_clamp GL\_SGIS\_texture\_edge\_clamp
> \> \> GL\_SGIS\_texture\_lod GL\_SUN\_multi\_draw\_arrays GL\_WIN\_swap\_hint
> \> \> WGL\_EXT\_extensions\_string WGL\_EXT\_swap\_control
> \> \>
> \> \> PTB-INFO: OpenGL-Renderer is ATI Technologies Inc. :: ATI Mobility
> \> \> Radeon X1400 x86/SSE2 :: 2.0.5529 WinXP Release
> \> \> PTB-Info: VBL startline = 1050 , VBL Endline = 2088805435
> \> \> PTB-Info: Measured monitor refresh interval from beamposition =
> \> \> 9.907484 ms [100.933797 Hz].
> \> \> PTB-Info: Will use beamposition query for accurate Flip time stamping.
> \> \> PTB-Info: Measured monitor refresh interval from VBLsync = 16.738390
> \> \> ms [59.742903 Hz]. (50 valid samples taken, stddev=0.031696 ms.)
> \> \> PTB-Info: Reported monitor refresh interval from operating system =
> \> \> 16.666667 ms [60.000000 Hz].
> \> \> PTB-Info: Small deviations between reported values are normal and no
> \> \> reason to worry.
> \> \> PTB-INFO: Using OpenGL GL\_TEXTURE\_RECTANGLE\_EXT extension for
> \> \> efficient high-performance texture mapping...
> \> \>
> \> \> WARNING: Mismatch between measured monitor refresh intervals! This
> \> \> indicates problems with rasterbeam position queries.
> \> \>
> \> \>
> \> \> ----- ! PTB - WARNING: SYNCHRONIZATION TROUBLE ! ----
> \> \>
> \> \> One or more internal checks (see Warnings above) indicate that
> \> \> queries of rasterbeam position are not properly working for your
setup.
> \> \>
> \> \> Psychtoolbox will work around this by using a different timing
algorithm,
> \> \> but it will cause Screen('Flip') to report less accurate/robust
timestamps
> \> \> for stimulus timing.
> \> \> Read 'help BeampositionQueries' for more info and troubleshooting
tips.
> \> \>
> \> \>
> \> \> The current version of Psychtoolbox that I'm using is:
> \> \> 3.0.8 - Flavor: stable - Corresponds to SVN Revision 640
> \> \> For more info visit:
> \> \> [http://svn.berlios.de/wsvn/osxptb/?rev=640&sc=0.](http://svn.berlios.de/wsvn/osxptb/?rev=640&sc=0.)
> \> \>
> \> \> I have also tried the beta version with SVN Revisions up to ( I think
> \> \> it was) 670 (the latest as of 2 days ago) with the same error. Using
> \> \> these same versions of Psychtoolbox on a colleague's computer my
> \> \> script runs fine.
> \> \>
> \> \> My system specs are: Dell Inspiron I6400 Genuine Intel (R) CPU T2500 @
> \> \> 2.00GHz 2.00 GB of RAM, Windows XP Version 2002. My refresh rate is
> \> \> set to 60Hz, and my monitor is set to 1.(Multiple Monitors) on ATI
> \> \> Mobility Radeon X1400 with a resolution of 1680x1050.
> \> \>
> \> \> I was wondering how to eliminate this warning sign, and also if this
> \> \> is indicative of deeper issues with respect to timing that I should be
> \> \> concerned about.
> \> \>
> \> \> Thank you very much for your help.
> \> \>
> \> \> Sarah Donohue
> \> \> Duke University
> \> \>
> \>