I have a 5870 video card in my 2010 Mac Pro. One mini displayport (mDP) is connected to a 27" ACD. Currently I have the second mDP connected through a mDP-to-VGA adapter to a 17" VGA monitor. Everything works fine.
I decided to free up the second mDP and reconnected the VGA through a VGA-to-DVI (I) adapter.
http://www.monoprice.com/products/p...=10419&cs_id=1041903&p_id=2396&seq=1&format=2
Again everything still works fine.
Now that the second mDP was free I tried to hook it to my Sony 32XBR6 to it with a a 15' HDMI cable connected to a mDP-to-HDMI DVI-I adapter.
http://www.frys.com/product/6311581
As soon as I connected the TV it displayed my desktop. Great, except for the fact that the VGA disconnected.
What I found is that I cannot seem to use the second mDP for HDMI and the DVI for VGA at the same time. I can use the main 27" ACD and the VGA (with the HDMI disconnected) or the main 27" ACD and the HDMI (with the VGA connected), just not all concurrently as a three-monitor configuration.
The physical connection of the HDMI disables the VGA but not the other way around. Detect displays or rebooting has no effect. I thought the 5870 is capable of driving three monitors albeit one of those monitors is through a HDMI connection. And I would think a 17" VGA cannot require that much "power" from the card couldn't handle it.
Now I suppose the problem could be the specific adapters I used. But considering they work independently I'm not inclined to blame them.
So does anybody have any idea what may be going wrong? Or is this just a limitation of the 5870 in a VGA/ADC/HDMI configuration?
I decided to free up the second mDP and reconnected the VGA through a VGA-to-DVI (I) adapter.
http://www.monoprice.com/products/p...=10419&cs_id=1041903&p_id=2396&seq=1&format=2
Again everything still works fine.
Now that the second mDP was free I tried to hook it to my Sony 32XBR6 to it with a a 15' HDMI cable connected to a mDP-to-HDMI DVI-I adapter.
http://www.frys.com/product/6311581
As soon as I connected the TV it displayed my desktop. Great, except for the fact that the VGA disconnected.
What I found is that I cannot seem to use the second mDP for HDMI and the DVI for VGA at the same time. I can use the main 27" ACD and the VGA (with the HDMI disconnected) or the main 27" ACD and the HDMI (with the VGA connected), just not all concurrently as a three-monitor configuration.
The physical connection of the HDMI disables the VGA but not the other way around. Detect displays or rebooting has no effect. I thought the 5870 is capable of driving three monitors albeit one of those monitors is through a HDMI connection. And I would think a 17" VGA cannot require that much "power" from the card couldn't handle it.
Now I suppose the problem could be the specific adapters I used. But considering they work independently I'm not inclined to blame them.
So does anybody have any idea what may be going wrong? Or is this just a limitation of the 5870 in a VGA/ADC/HDMI configuration?