DVI Port Adapter Question on a 2009 Mac Pro

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DVI Port Adapter Question on a 2009 Mac Pro

Recently my company switched out desktops for operational purposes. I was tasked to re-purpose a 2009 Mac Pro tower for simple video cue playback.

I found a single-link DVI to VGA adapter, and plugged it into the DVI port with a VGA cable going into the video input. I was not able to get a display out of the Mac. I tried with another MiniDisplay to VGA adapter, and it works fine. However for operational reasons I cannot use that adapter.

I read the manual again, and it did state that connecting to either port should work: (Page 13)

https://manuals.info.apple.com/MANUALS/0/MA914/en_US/Mac_Pro_Early2009_4707_UG.p df

As I am not able to gain access to parts easily, unfortunately I have no other adapters to test with.

What is the problem here? I can only assume that a single-link DVI connector would be enough for converting video signal into an analog VGA output. Is the adapter not suitable, or is there somewhere in software settings that I need to adjust (switching display port on the GT120 card, etc.)?

The Mac Pro in question is a 2009 version with a GT120 card that has a MiniDisplay port and a DVI port. The OSX version is the very old 10.4.x that is unlikely to get upgraded in the near future, nor does it have internet access of any sort...

Thanks in advance for all your help!

Mac Pro, Mac OS X (10.4.9), Company computer

Posted on Jul 30, 2015 12:32 PM

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Answer 1

lllaass

Level 10

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Jul 30, 2015 12:40 PM in response to tsuen

Does the DVI output work for a DVI-input monitor? Maybe a bade DVI output

Does the DVI>VGA adopter work on another computer? Maybe a bad adopter

There is no software settings.

I have a GT 120 on my 2009 Pro and use a DVI>VGA adopter with no problems and have used a mini displayport output too.

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Answer 2

Jul 30, 2015 3:21 PM in response to tsuen

A so-called "VGA adapter" from DVI has NO electronics, and is NOT a converter. All the signals required for VGA are available on the DVI-I connector, and those signals should be produced by your Display card:

Graphic from wikipedia.com

They are the bar and the four pins around it at one end of the connector, plus a few pins from the top row adjacent (Salmon Pink in the diagram). The diagram can be displayed a little larger if you click on it.

But -- you can not "stack" adapters. Attach a DVI cable directly to the computer port, and the VGA signals will NOT be carried through the cable.

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Answer 3

tsuen Author

Level 1

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Jul 31, 2015 8:53 PM in response to lllaass

Thank you for your reply! It is indeed a good point to test. I shall try to find a monitor with DVI input to test later.

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Answer 4

tsuen Author

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Jul 31, 2015 8:55 PM in response to Grant Bennet-Alder

Thank you for your reply. The DVI to VGA adapter connects the port and the VGA cable, which is in turn plugged into the video input. Hopefully I am able to find a DVI monitor to test soon.

Thanks for clarifying the terminology!

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Answer 5

tsuen Author

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Aug 4, 2015 2:19 PM in response to tsuen

Tested a DVI monitor with a DVI-D cable. The Mac tower detects the display with no problem. However the single-link DVI-I to VGA adapter does not work. Tried with another DVI port on other computers too; the adapter does not seem to be the culprit.

Out of curiosity, is the GT120 outputing digital signal only (DVI-D)? Or is it a DVI-I output that contains both analog and digital information?

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