# Backwards compatibility? **URL:** \ **Category:** Uncategorized\ **Created:** [December 2, 2005, 8:42pm UTC](https://psychtoolbox.discourse.group/t/backwards-compatibility/1234 "2005-12-02T20:42:36Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![kathryn\_devaney](https://avatars.discourse-cdn.com/v4/letter/k/90db22/32.png) [@kathryn\_devaney](https://psychtoolbox.discourse.group/u/kathryn_devaney)\ **Post date:** [December 2, 2005, 8:42pm UTC](https://psychtoolbox.discourse.group/t/backwards-compatibility/1234/1 "2005-12-02T20:42:36Z")
Hi, I am trying to run code that was written in OS9 on my powerbook, which runs OSX. I (maybe foolishly?) assumed that newer versions od psychtoolbox would be backwards compatible. However, every time I try to debug&run the program, it starts fine (there's a little dialouge box at the beginning) then switches to a solid blue screen, which I need to force quit Matlab to get out of. Since I have to force quit, I can't see what the error is, but I know that this program runs perfectly in OS9. I am also (perhaps needless to say at this point) brand new to matlab and to programming in general (this is someone else's code) so there could be some kind of glaring error in the code and I really wouldn't be able to catch it. So, code works in OS9, does not work in OSX - does anyone have any ideas about what could be going wrong? Thanks much, Kathryn ---
**Author:** ![kathryn\_devaney](https://avatars.discourse-cdn.com/v4/letter/k/90db22/32.png) [@kathryn\_devaney](https://psychtoolbox.discourse.group/u/kathryn_devaney)\ **Post date:** [December 4, 2005, 12:32am UTC](https://psychtoolbox.discourse.group/t/backwards-compatibility/1234/2 "2005-12-04T00:32:14Z")
Hello all, I thought I was having a backwards compatibility issue, but it turns out to be larger than that: Evey time the command "Screen('OpenWindow')" is encountered, a solid blue screen appears and the computer freezes. I sometimes get a red screen with a big warning symbol too. The only way to get off of this screen is to force quit matlab. I am running MacOSX (Tiger) and Matlab 7.0.4 and the most recent version of Psychtoolbox. I have tried reinstalling Psychtoolbox, which didn't help. I'm not sure what else to do - has anyone else run into a situation like this, or does anyone have an idea about what might be going wrong? Any suggeestions would be much appreciated. Thanks, Kathryn ---
**Author:** ![kathryn\_devaney](https://avatars.discourse-cdn.com/v4/letter/k/90db22/32.png) [@kathryn\_devaney](https://psychtoolbox.discourse.group/u/kathryn_devaney)\ **Post date:** [December 5, 2005, 7:23am UTC](https://psychtoolbox.discourse.group/t/backwards-compatibility/1234/3 "2005-12-05T07:23:44Z")
I found this tidbit, in part of an explanation of what the Screen('OpenWindow') command does: It performs a couple of checks to make sure that synchronization to the vertical retrace, queries of rasterbeam positions and a couple of other timing related functions work properly on your specific setup. You will see a blue screen for multiple seconds while this checks are performed. If a check fails or gives potentially troublesome results, PTB will flash a big yellow or red warning triangle on your display and provide a detailled trouble report on the Matlab command window, together with troubleshooting tips. (from Sec 4.2.1 of [http://www.kyb.tuebingen.mpg.de/bu/people/kleinerm/ptbosx/](http://www.kyb.tuebingen.mpg.de/bu/people/kleinerm/ptbosx/) ptbdocu-1.0.5MK4R1.html ) This is \*exactly\* what is happening with my computer, except it also freezes when I get the warning, so I do not get the trouble report. ---
**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 5, 2005, 4:29pm UTC](https://psychtoolbox.discourse.group/t/backwards-compatibility/1234/4 "2005-12-05T16:29:14Z")
Do you have two monitors plugged in. I don't think that 2 dispalys work with the toolbox for all video cards (or any?). I just now started to port old psych toolbox stuff to OS X and the 1st problem was like you mentioned. I unplugged my second monitor and got a bit further. Not much though, but I thought I'd mention it. Ethan > --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "kathryn\_devaney" \ wrote: > \> > \> I found this tidbit, in part of an explanation of what the Screen('OpenWindow') command > \> does: > \> > \> It performs a couple of checks to make sure that synchronization to the vertical retrace, > \> queries of rasterbeam positions and a couple of other timing related functions work > properly > \> on your specific setup. You will see a blue screen for multiple seconds while this checks > are > \> performed. If a check fails or gives potentially troublesome results, PTB will flash a big > yellow > \> or red warning triangle on your display and provide a detailled trouble report on the > Matlab > \> command window, together with troubleshooting tips. > \> > \> (from Sec 4.2.1 of [http://www.kyb.tuebingen.mpg.de/bu/people/kleinerm/ptbosx/](http://www.kyb.tuebingen.mpg.de/bu/people/kleinerm/ptbosx/) > \> ptbdocu-1.0.5MK4R1.html ) > \> > \> This is \*exactly\* what is happening with my computer, except it also freezes when I get > the > \> warning, so I do not get the trouble report. > \> ---
**Author:** ![mariokleiner](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@mariokleiner](https://psychtoolbox.discourse.group/u/mariokleiner)\ **Post date:** [December 6, 2005, 2:51pm UTC](https://psychtoolbox.discourse.group/t/backwards-compatibility/1234/5 "2005-12-06T14:51:52Z")
Hi, this is the state of 2 displays support: a) If you use 2 displays to show two different stimuli (e.g., stereoscopic stuff) in two different onscreen windows, you should be fine, but see c) b) If you only use 1 dispay for stimulus presentation, its better to put the 2nd one in mirror mode or switch it off/unplug it, because presentation timing/jitter gets worse if you have your desktop/Matlab on the second screen - thats a technical limitation of the graphics hardware. c) If you use an ATI graphics card on a dual-display setup with OS-X before 10.4.3 "Tiger", you may have trouble, because the ATI drivers contain a bug that can affect syncing/timing that's fixed in 10.4.3 earliest - I think. I don't have ATI cards so i can't test myself, but the sync tests should spot this problem. Single display support: Should always work, except you use OpenGL-stereo mode on gfx-hardware with not enough VRAM. If you have trouble with failing sync-tests/OpenWindow and such, that don't relate to anything above, please read the error-output of PTB in the Matlab window and follow the troubleshooting tips displayed. If that fails as well, please report bugs as precise/detailled as possible, including your hardware setup, display setup, display settings and preferrably a small script that shows the bug. Every minor detail can help spot the problem. best, -mario > --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "ethan\_montag" \ wrote: > \> > \> Do you have two monitors plugged in. I don't think that 2 dispalys > work with the toolbox > \> for all video cards (or any?). > \> I just now started to port old psych toolbox stuff to OS X and the > 1st problem was like you > \> mentioned. I unplugged my second monitor and got a bit further. Not > much though, but I > \> thought I'd mention it. > \> > \> Ethan > \> > \> --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "kathryn\_devaney" > \ wrote: > \> \> > \> \> I found this tidbit, in part of an explanation of what the > Screen('OpenWindow') command > \> \> does: > \> \> > \> \> It performs a couple of checks to make sure that synchronization > to the vertical retrace, > \> \> queries of rasterbeam positions and a couple of other timing > related functions work > \> properly > \> \> on your specific setup. You will see a blue screen for multiple > seconds while this checks > \> are > \> \> performed. If a check fails or gives potentially troublesome > results, PTB will flash a big > \> yellow > \> \> or red warning triangle on your display and provide a detailled > trouble report on the > \> Matlab > \> \> command window, together with troubleshooting tips. > \> \> > \> \> (from Sec 4.2.1 of > [http://www.kyb.tuebingen.mpg.de/bu/people/kleinerm/ptbosx/](http://www.kyb.tuebingen.mpg.de/bu/people/kleinerm/ptbosx/) > \> \> ptbdocu-1.0.5MK4R1.html ) > \> \> > \> \> This is \*exactly\* what is happening with my computer, except it > also freezes when I get > \> the > \> \> warning, so I do not get the trouble report. > \> \> > \>