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Want to download the latest version of Screen Spanning Doctor (v0.3.3) or visit the forum?
Here is a list of supported machines.

Use an extended dektop with your iBook, iMac or eMac

Please note that I cannot be responsible for any damage that you might do to your computer. This site is for educational purposes only and you are responsible for everything you do with the given information. The information published here may not be used for commercial purposes without written approval from!

Update 05/02/05

Mac OS X 10.4 Tiger

I updated Screen Spanning Doctor (0.3.3) to support Tiger.

If you installed the patch prior to updating your OS you don't need to reinstall the latest version of the patch since only the installation program was changed to work in Tiger.

I also decided to pack the program into a disk image to avoid frequent problems with StuffIt extracting an unusable program from the .sit file and because StuffIt Expander is no longer included with Mac OS X.

Update 11/14/04

iMac G5 and new iBooks

Apple released the all new iMac G5 a couple month ago and by now it's been shipped to many customers.

At this time I would like to announce that it is confirmed that the new iMac G5 can do screen spanning after being patched with Screen Spanning Doctor.

The same is true for the speedbumped iBooks released in October (no surprise here since the architecture of the iBook hasn't changed).

Unfortunately I cannot find enough time to work on the redesign of this website so I'll take a little longer than expected.

Update 06/11/04

New eMacs and iBooks

Unfortunately this update has been delayed quite a bit (welcome to the Apple world ;)

In the meantime Apple has released a new iBook and eMac lineup and I am happy to report that the Screen Spanning Doctor will remain work on these new models.

I spent some time setting up a new server for this project. The server is running nicely and already serves this page. I'm also in the process of renewing the website to make it more readable as the current concept causes this page to be quite long and I doubt that most readers read all the way through it.
It'll still be a while till I have enough time to finish the redesign but it should be coming this summer.

Update 01/12/04

iMac 20"

I am very happy with the new forum. In a very short time there have gathered some very helpful and knowlegeable people and I'm glad that they are helping out. Thanks to all of you!

There's not much new since the last update. The only new Mac is the 20" iMac - and yes, it does work with the patch!

I corrected a small bug in Screen Spanning Doctor, that prevented it from enabling clamshell mode on G4 iBooks. Users of G3 iBooks don't need to care about this update but if you own a G4 iBook and want to use clamshell mode you should download and run the latest version.

Since I had so many nice people offer donations I finally decided to open a PayPal account.
This site and the Screen Spanning Doctor will of course remain to be free - but if you wish to support this project through a donation you can now do this.
Just click the "Make a Donation" button on the top of this page. Thanks to all supporters!

Update 11/19/03

New Forum.

I decided to set up a forum because I get so many emails that I can hardly read them all. Especially in the last month or two this led to very long delays before I could reply. The questions in 90% of the emails I get could easily be answered by other readers (most of the answers are on my website anyways) so I think that this forum will give you the opportunity to get answers to your questions faster than through writing me. I hope that many readers will join me in answering questions or posting tips and tricks they figured out.

You don't need to register to read or post in this forum, but you may if want (you then can edit your posts).
Since almost anybody can (more or less) speak and read English (but only a few know German, Frensh, Spanish or Japanese) you should try to post in English as well.

Please read all of this page and check/ask the forum before you email me. I'll try to answer your questions there as long as I have time but I hope that others will join in. You can still email me if you don't get an answer there or if you have an urgent question.

Here's the new forum.

Update 10/27/03

Panther compatibility and the new iBook G4.

From the feedback I have received so far regarding the new iBook G4 I can say that the Patch does work with these new machines. This obviously means that spanning also works in Panther (Mac OS 10.3). However, to get it to work in Panther you need to either apply the patch via my program (for those that already received a copy by email) in Jaguar before you upgrade or you need to apply the manual patch in Open Firmware. The old beta version of my Program won't launch in Panther (due to AppleScript restrictions).
The good news is that as of today I'm offering a downloadable version of my program that is Panther compatible. This version will also work in Jaguar.
If you already applied either the manual patch or the older betaversion of my program you don't need to use the new program again since the actual code that is stored in the nvram hasn't changed.

Since I get so many emails asking if the patch also allows external resolutions higher than 1024*768 I want to clarify this: Yes, you can select much higher resolutions. If you use Panther you will see that you get a lot more refresh rates compared to Jaguar. This is especially good for people who want to use a 19" CRT with the optimal resolution of 1280*960 which is now available with up to 120 Hz (in Jaguar this was limited to 75 Hz - not only for the iBook but also for PowerBooks with ATI graphic chips).

Click here to download Screen Spanning Doctor
Use at your own risk!
If you have problems or suggestions regarding the new program, iBook G4/Panther compatibility or anything else you can send me an email but please read the whole page before you write to make sure the answer to your problem isn't already discussed here.

One more thing: The iMac 15" 1 Ghz now is also confirmed to work with the patch.

Update 09/23/03

Some information about the newly released iMacs and some more.

I have received some feedback from owners of the newly released 1.25 Ghz 17" iMac and I'm glad to report that the patch will work on those machines. I haven't received any feedback regarding the new 1 Ghz 15" model but I think the patch would work there as well. If you are a lucky owner of one of those iMacs please send me your feedback.

A note for those still willing to do the maual patch (not the AppleScript one): You need to plug in your AC adapter when you enter the code in Open Firmware. Without AC power the nvstore command won't work.

Unfortunately I've not been able to respond to email within a decent time in many cases lately. Please be advised that it might take me a week or so to get back to you. I try to reply to all email but since my mailbox is constantly overflowing it tends to take some time. I apologize for any inconvenience. Please read the whole page before asking me questions to avoid unnecessary work.

The final version of my AppleScript patch will be available for download soon. The beta didn't reveal any issues so the final version will be functionally the same as the beta that I sent out to many readers already (those who applied the patch already - by either entering it manually or with the beta script won't have to use the final version again).

Update 07/31/03

A word about scripts and a possible solution for dead iBooks.

The German computer magazine c't released an AppleScript that enables screen spanning. It does pretty much the same as my patch. However, it doesn't warn you about the risks. As a result there's a new wave of dead Rage-based iBooks.
This is the reason why I didn't release a program to automate the process. The problem is that a program or AppleScript will lower the inhibition threshold. People don't think about the possible consequences as they would if they have to enter the code manually.
But since there now is a program to do the job and since it's not a very good one (not available in English either) I decided to release my own AppleScript to do it right.
Since I never really tested it except on my own iBook (900Mhz 12") I can't say if it will work in every case but it showed no problems here.
On iBooks it will also enable clamshell mode which was not available previously (clamshell mode behaves a bit weird sometimes at least with the TV adapter - couldn't test it with a real monitor and external keyboard yet). The program can also be used on some iMac and eMac models (see list linked below). If you wish to get a copy please email me.
Just to make it clear to everyone: this script won't enable spanning on any machine that wasn't supported so far but it should work with every supported Mac (see this list).
The script checks if you have a supported machine as a security measure and should display a message that it won't run on your Mac. However, if you know your machine is not supported you shouldn't try this program either.

There might be a solution for dead Rage-based iBooks. So far this has helped at least one iBook owner:
1) remove battery, leave ac adapter plugged in
2) hold down the Apple key and press the power button
3) you should hear the startup chime - keep the buttons pressed until you see the open firmware interface
4) type reset-nvram and press enter (for international keyboards the keys might be in a different location than expected)
5) type reset-all and press enter
6) your iBook should now boot normally
If anybody had success with these instructions please let me know.

Update 07/18/03

After about 2 months another quick update.

Throughout the last month I have received several reports regarding the new eMac. Fortunately they all said that the patch worked fine without any further modification (that is for the eMac models released this Spring that have a 133 Mhz system bus and ATI Radeon 7500 graphics - the older eMac with 100 Mhz system bus and GeForce2MX is not supported).

I think it's time for a little summary of supported and unsupported systems since I keep getting emails asking if a specific model would work or not.
You can find a (hopefully) complete list here.

Update 05/15/03

Some News for those who are interested in the newly released Macs and some resolution clarification.

The patch also works with the 17" iMac 1 Ghz and the new 800/900 Mhz iBooks. I don't have any info about the eMac with Radeon 7500 yet but I expect no problems with this machine either (the old eMac did not work though).

In the past the question about available resolutions came up a few times so I want to clear things up:
When you install the patch you not only get the ability to use an external monitor to extend your desktop but you also get to choose the external resolution. It's no longer limited to the internally available resolutions. Most resolutions that are available on Powerbooks or Powermacs will be available on your iBook or iMac. Depending on your specific model you might not be able to use a certain resoltion that might be there with another machine though.
This patch does not allow the iBook to operate in clamshell mode (operate with the lid closed) and it doesn't allow you to turn off the internal display either.

If you have problems with certain monitors or resolutions (or their unavailability) you should try SwitchRes by Stephane Madrau. This tool enables resolutions that might be unavailable for some reason. Please let me know if SwitchRes helped resolve your issues.

Update 01/25/03

This update is only relevant to those of you who use LinuxPPC besides Mac OS.

When you use Linux besides Mac OS on your iBook you will notice that after you apply the patch you can't boot into Linux anymore. If you reinstall Yaboot the patch doesn't work anymore but you can boot into Linux again.

The problem is that the patch selects the root device with select-dev but doesn't release it once it's done.
To solve this problem I added another line containing unselect to the patch code.

If you tried the patch already and experienced this issue you should zap the NVRAM and enter the whole patch again as listed below. You could also add the extra line in nvedit but you should only do that if you're familiar with the Open Firmware as you can easily make a mistake.

If you don't have the problem you don't need to change anything but if you apply the patch for the first time you should use the new code as shown below.

Update 12/21/02

This is just a quick update. I didn't have much time lately so it's been a while since I posted news here.
The new iBooks released Nov. 7 fully support this patch. The procedure is the same as for the original Radeon iBooks (see below). If you have the 800 mhz version with 32 MB VRAM you don't need to modify the settings for Quartz Extreme support in it's config file. If you have the new 700 mhz version you still need to do this though.
The newest iBooks use the Radeon Mobility 7500 (in System Profiler it's listed as RageM7).

The same patch can also be used to enable dual head mode for the 17" iMac. I have verified this myself a little while ago. Since the GeForce4MX uses 32 MB VRAM you also don't need to change the settings for Quartz Extreme as it will be enabled by default.

Some people have asked if there is a way to test if the iBook will be able to use the patch without applying it permanently. Well, permanently until you zap the nvram but there were cases with Rage-based iBooks where storing and enabling the patch caused the iBook to stop working and not even zapping the nvram helped.
So for all of those who want to make sure the patch will work with their iBook can simply enter the following in Open Firmware (please read the whole page before you do this):

1 " /" select-devreturn
2 00000000 " graphic-options" get-my-property 2drop !return
3 mac-bootreturn

This will enable dual head mode only once (until you reboot). You might still have to disable mirroring in the 'Displays' pref pane. You can find this option under the tab 'Arrange'. If 'Arrange' is not there then the patch doesn't work with your iBook or you entered it incorrectly.

Original Article

Ever wondered why your new iBook (16MB VRAM) can't display an extended desktop on an external screen even though it has a Radeon chip that does support this feature?

Well, for some reason Apple decided to lock this function.
The good news is that I've been working on a solution for some time now.
At first I discovered how to enable an extended desktop (also called screen spanning or dual head mode) with a trick in Mac OS 9.
This, however, didn't satisfy me and many others for too long because I like to use Mac OS X. So I went at it and found a solution.

I assumed that the ATI driver reads the value of a variable defined in the Open Firmware and decides, depending on the value of that variable, whether to limit the external screen to mirroring.
The key was to find that variable and to change it to a value that would cause the driver to allow the dual head feature. I was lucky and found the variable and came up with a firmware script that changes this variable every time you turn on your iBook.

Since this hack is done in Open Firmware it works with both Mac OS 9 and Mac OS X. I used my iBook with dual displays for a while in OS X and OS 9 and didn't experience any problems.

This patch works with current iBooks, which have the ATI Radeon Mobility (sometimes reffered to as RageM6) only. According to the Apple Store these are the model numbers of the supported systmes: M8600*/A, M8602*/A, M8603*/A.

Apple System Profiler should give you the following information:

From the feedback I received so far I can conclude that the iMac G4 15", the eMac and older iBooks without the Radeon Mobility chip do not support this feature. I doubt that there will be a solution for these systems in the future (please read this page for additional information).
Chances for a firmware based solution for the 17" iMac are good. I was able to use an extended desktop in OS 9 already (with the 'old' method of swapping rom files).
I hope to present a solution soon.

Please note that the 17" iMac and the new iBooks with Radeon Mobility 7500 are now also supported. The part numbers above as well as the screenshot are for the 600/700Mhz iBooks with original Radeon Mobilty and 16MB VRAM. See the 12/21/03 update above for details.

Don't use this patch with ATI Rage based iBooks!
They could possibly die!

Since the patch didn't enable dual head mode on any Rage iBook (based on reader feedback) it's not worth to take the risk of possibly damaging your iBook.
This accounts to Rage iBooks only. There haven't been significant problems with the Radeon iBooks. The only problems noted for those iBooks were that it simply didn't enable dual head mode but I suspect that the few who reported this did something wrong in applying the patch. Their iBooks were not damaged.
Please read this page for additional information.

The Patch

Since this patch is done in Open Firmware you have to boot your iBook with pressed Command-, Option-, O- and F-keys.

At the command line promt you have to enter the lines exactly as they appear in the gray box below (including spaces and quotation marks).
means you have to press the space bar.
return means you have to press the return or enter key.
ctrl-c means you have to press the ctrl- and the c-key.
00000000 are eight zeros, not o's!

Caution: The command line doesn't interpret international keyboard layouts. If you use a keyboard version other than english you might have to press other keys to achieve the appropriate character.

Please note that you won't get any feedback after you enter the 2nd and 3rd line. The line will just appear cleared. That is normal behavior (it's like a text editor that only displays one line so after a carriage return you will be at the next line which will be empty until you type something).

  Command + Option + O + F
1 nveditreturn
2 " /" select-devreturn
3 00000000 " graphic-options" get-my-property 2drop !return
4 unselectreturn
5 ctrl-c
6 nvstorereturn
7 setenv use-nvramrc? truereturn
8 reset-allreturn

The last command will restart your iBook.
If you replace 00000000 with 00000008 you will also unlock clamshell mode for iBooks.

In case you want to return to your original configuration all you have to do is reset your nvram. This is usually done by pressing the Command-Option-P-R keys while you turn on your computer until the start sound chimes again. If you need more information on this you can search Apple's KBase (I'll add a direct link later when I have more time).

After this patch Quartz Extreme will not be active while using two screens if you have a machine with 16 MB VRAM. This is the same problem as with the Powerbook G4 with 16 MB VRAM. You can fix this issue by changing the value of


in the file

System/Library/Frameworks/ApplicationServices.framework /Versions/A/Frameworks /CoreGraphics.framework /Versions /A/Resources /Configuration.plist

from 16 to 8.

You need special privileges to save changes to this file. You can either do it in OS 9 or log in as root. You can also temporarily change the owner of the file. Use the "Get Info" command in Finder to make yourself owner of the file (remember who owned it before). Then open it with any plain text editor or, if you have the Developer Tools installed, with "Property List Editor". Change the value and save the file. Now you can change the owner back to the one originally set.

The TV adapter mentioned at this site before (see link below for older version) only works in OS 9 since the PAL/NTSC resolutions are not available in OS X (I hope to fix this soon).

If you have any suggestions or additions I would appreciate an email from you:
If you tried this with a different version of the iBook or iMac (although it is not reccomended to do so) it would be nice if you would let me know if it worked or not so we can share this information with the Mac community.

Click here to view an earlier version of this site with instructions for enabling screen spanning in Mac OS 9 without a firmware tweak.

Please note that I cannot be responsible for any damage that you might do to your computer. This site is for educational purposes only and you are responsible for everything you do with the given information. The information published here may not be used for commercial purposes without written approval from!

Last updated: 05/02/05 2002-2005