Two Monitors on iMac With Free Screen Spanning Software

It is possible to install an extra monitor on an iMac G5 computer and have what is known as “screen spanning” which is an extended desktop mode of operation.

New LCD Widescreen Flat-Panel Monitor Recommendations

Screen spanning is where your screen desktop area is extended to include the extra monitor (not a duplicate of your existing display). There is a small Apple mini VGA to regular VGA plug short adapter cable that is required to go from the small VGA port on the back side of the iMac computer and plug the other end into the monitor cable.

The original Apple OS X software for the iMac G5s did not provide screen spanning capabilities. The hardware can handle it, but Apple chose not to enable it in the software. Not sure the reason behind Apple’s decision on that. Apple only supported dual monitors with both monitors displaying the same information on the screens at the same time. However, there is a free software modification that can make use of the hardware capabilities of the internal video card on the motherboard in the iMac G5 computers. The video card on the iMac G5 20 is a built-in nVIDIA GeForce FX 5200 directly mounted on the motherboard. The iMac motherboard essentially provides the means to have two monitors using the Apple Mini-VGA to VGA Display Adapter for a Mac. The mini-VGA adapter will cost you somewhere around $20.00, including shipping charges, to purchase from Amazon. You might be able to buy one for a little bit less.

You can download the latest version of the Screen Spanning Doctor (v0.3.3) software. Screen Spanning Doctor (0.3.3) supports Tiger. Click on the link to be sure your Apple computer is compatible and able to make use of this software mod. The software patch was for the iBook, eMac, and iMac computers. You can view which models are supported. Please note, the site has the following disclaimer that I would also have to echo too:

“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 cool part about this addon monitor screen spanning mode of operation, is it can have its own separate monitor configurations for screen resolutions, and even the background picture for the desktop can be different too. The screen saver program can display different designs on each monitor. It doesn’t mean you can have different screen savers running at the same time, it just means that a Screen Saver like Cosmos, which has different images from the universe, each monitor will display a different image at the same time. I personally have installed the screen spanning software on my iMac G5 and it works terrific for me.

If you are thinking to use an extra monitor because your Apple iMac G5 20 or iMac G5 17 inch is having main display problems, your problem might actually be a bad motherboard. The capacitors for the video display unit located on the iMac G5 Mainboard go bad (burst open, leak electrolytic fluid, and dry up) along with additional filtering capacitors that blow up on other areas of the motherboard. Refer to the article I wrote about How to Repair Apple iMac G5 Motherboards and replace those bad capacitors. Or, the problem may be with your Apple Power Supply Unit.

When an extra monitor is plugged in to the port on the back of the iMac G5, the Apple software senses a new monitor is installed and provides the available screen resolutions for each, on each monitor. So, when you go to System Preferences, and click on Displays, the configuration settings appear on each of the monitors’ screens with each specific configuration particular to each monitor. Arrangement of the monitors can be on the left, right, top, or bottom by simply dragging the monitor to the position you would like. If you decide to have your monitors stacked on a shelf, one above the other, you can place the monitors under one another on the setup screen. If you wish to have them on your desktop, side-by-side, then place the setup screen on the left or right. When your monitors are set up the way you want, the mouse will track accordingly. For example, if you have your monitors side-by-side, then when you move your mouse to the right, you will then go over to the other screen. This is handy if you regularly have lots of windows open and wish to expand your Mac desktop area. Or, you can have one application on display on one screen and have another running on the other. Just drag the open software application screen to the other monitor. Colors can also be calibrated between each of the screen monitors too.

With the price on large screen LCD monitors having dropped significantly over the years, now is the time to add more real estate graphic exposure to your desktop area today.

Speaking of more graphic exposure, get your business discovered online with Professional Web Services, Internet marketing services. Learn how we can help grow your business on the Internet. Start earning more sales and gaining qualified leads from your website today. Find out how your website can work for your business as a super online sales and marketing tool.


Hi Jim

Great site!

I've been using the screen spanning doctor for a couple of years now on my iMac G5 1.8ghz (ambient light version).

But a few months ago, the second monitor, a Mitsubishi Diamondcrysta RDT156V went dark. It was still powered on, and detected on the imac under displays, but it was dark.

I couldn't see anything, so I don't think it was simply the backlight (which you can usually see something faintly). I figured it was the monitor. But then it came on. It did this a few times, on for a few hours, then off again.

Restarts, resetting pram, nvram, etc. had no effect. nor did reinstalling and uninstalling spandoctor several times.

i was ready to pick up a new monitor, since the mitsubishi was about 5 years old and I figured it was just not up to the task anymore, but then I tried it on my trusty Pismo. It worked! And is working still. no flicker, no darkening, not even once.

so i plugged it back into my imac and no good. still dark. hmm. So, i assume I must have done something to my logic board on my imac for it to not display on the second monitor. The main monitor on the imac is fine. no probs at all. never had any. but the second monitor when plugged in, is recognized in displays, detected with all the options listed, but is dark. This is true of mirroring and no mirroring.

It's getting the signal, but remains dark. I then guessed it might be the VGA to MiniVGA connector since I heard they are finicky and I've had to replace one in the past already. Replaced it. No change.

I'm stumped.

Any clues? I'm resigned to thinking it's a logic board prob on the imac.

David George


Thank you for the great information! I have used your training to repair several flat-panel monitors, system board, etc., by replacing visibly bad capacitors.

On my plate at the moment is an older iMac G5 PPC (20″, 1.8 GHz, 2 Gig Ram) that is still usable, although very quickly becoming obsolete in the WEB environments. It has the bulging capacitors on the system board, but still works fine. The owner suffered a hard drive failure and gave me the unit after I recovered her data from it. I have put a 128 Gig SSD (GSkil 2.5″) I had laying around in it and reinstalled the OS and applications.

With the SSD it runs GREAT! It’s fast enough that it’s a real shame to discard the unit. So I’ve decided to go ahead and replace all the capacitors on the system board and the power supply. Later I may disassemble the unit and sell it for parts. Until then… Two ideas have come up with this unit and I haven’t found anything online addressing them:

1) What would it take to make an adapter cable to wire directly into the monitor so it can be used as “just a monitor” for another machine? I guessing opening up one of Apple’s other 20″ “monitor only” units would clue me in, but I don’t have access to one.

2) I would love to gut the inside of this unit and install a generic Intel laptop or micro board in there. I imagine I could find a newer iMac G5 with an Intel board and perform a swap, but that’s probably going to being pricey at best.

Do you have any experience or advice on these two ideas?

I am thankful for all the service you’ve provided to us!


David George
IT Consultant
Houston, TX

Jim Warholic


Thank you for your comments.

To address point #1: The problem with trying to use the monitor, just as a remote monitor, is problematic. The drive circuits are off of the main logic card. So, I haven’t heard of anyone doing that.

To address point #2: I don’t think that is a realistic possibility, given point #1,

Cool about the SSD. I wish these were cheaper.



Your email address will not be published. Required fields are marked *