Problems detecting monitor type (or ID)

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Level 2

499 points

Problems detecting monitor type (or ID)

I have a 12" PowerBook G4 (Early 2006, 867 MHz model) onto which I am trying to connect a Sony LCD display (SDM-X73) through the VGA port. But I have a problem where sometimes the monitor is indeed recognised as an "SDM-X73", while other times it is recognised as a "VGA Display". On rare occasions, the display isn't recognised at all and I have to reboot the laptop in order to make the display work again.

I have gone and bought another mini-VGA to VGA adaptor just to verify that the cable is not at fault, and it indeed is not the case—with the original and the new cable, the computer has the same difficulty recognising the type of the attached monitor.

In short, why would the computer have this inconsistent behaviour in detecting the monitor type connected to it? It is a small issue because it affects what resolutions and scan rates can be selected in the Displays preferences, and it also causes the computer to select the default ColorSync colour profile for the monitor every time the type changes. Is this a sign of the computer system developing a bad video output port?

A few more details about the laptop in question: it has 640 MB of RAM installed, it's running Mac OS X 10.5.8 Leopard and it's all otherwise original equipment. The software I run on it is pretty bare-essential: Safari, Mail, iWork '09, a Wacom Graphire 4 tablet driver and PasteBot Sync. I don't have any 3rd party software that relates to displays.

Any ideas? Thanks!

--tonza

Posted on Aug 4, 2011 6:16 AM

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Answer 1

tonza Author

Level 2

499 points

Aug 12, 2011 7:48 AM in response to tonza

Figured it out...

I don't know whether it is a fault or limitation in either the video card in the PowerBook G4 or the video port(s) (and associated electronics) on the monitor itself, but the monitor has to be driven by the PowerBook at 60 Hz before the monitor ID comes across correctly.

I had my monitor set to 75 Hz, which caused problems in identifying the monitor. The fix is to open the Displays system preferences and set the external monitor to operate at 60 Hz for all resolutions. This allows the monitor ID to be retrieved by the video hardware properly, and the Displays system preferences (and the system menu for it) will show that.

It must be noted that this happens to be the case for my computer and external monitor--it may not apply to your setup, but then again, it may if you are having similar problems with monitor IDs.

--tonza

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