# ptb error

**URL:** https://psychtoolbox.discourse.group/t/ptb-error/905
**Category:** Uncategorized
**Created:** [December 19, 2008, 8:25pm UTC](https://psychtoolbox.discourse.group/t/ptb-error/905 "2008-12-19T20:25:44Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)
#### Post date: [December 19, 2008, 8:25pm UTC](https://psychtoolbox.discourse.group/t/ptb-error/905/1 "2008-12-19T20:25:44Z")

</div>

Hi,  
  
I am new in psychtoolbox and when I try to run Screen.m on a MAC OS X  
with ATI Radeon HD 2600 Pro and i get the following error:  
  
  
%%%%%%%  
WARNING: Couldn't compute a reliable estimate of monitor refresh  
interval! Trouble with VBL syncing?!?  
  
  
----- ! PTB - ERROR: SYNCHRONIZATION FAILURE ! ----  
%%%%%%%%%  
Previous posts suggest solutions for Windows machines. Any suggestion  
for mac users?  
  
Moreover., my experiments are on decision making and therefore  
millisecond precision is not needed. Could i continue by forcing it to  
skip the test (Screen('Preference','SkipSyncTests', 1);  
  
Thanks  
  
George