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Can't get 1080p on third monitor

P

poisoncoyote

macrumors newbie
Original poster
Nov 23, 2012
7
0
I just got a new 39" 1080P HDTV and want to use it as a 3rd monitor.

I'm running the latest version of Mountain Lion. I am using the ATI Radeon HD 5770. The card has two mini display ports and one DVI port. On the two min DP ports I have active DVI converters to my normal monitors. The third DVI port I have connected to the TV with a DVI -> VGA cord.

The HDTV comes up fine but at a resolution of 1360x768. I know that VGA can do 1920x1080 so I don't understand why it won't work.

I had a spare mini DP -> HDMI cable that I then tried on the HDTV and that made it display in 720p. It also killed my 3 monitor setup due to the active converters. (I started to wonder if the TV could do 1080p at all. Plugged in my PS3 and it came up 1080p.)

So I don't know what else to try. I considered trying a DVI -> HDMI converter as a last resort. Any other ideas or tricks to make my Mac output 1080p to this HDTV?
 
poisoncoyote said:
I just got a new 39" 1080P HDTV and want to use it as a 3rd monitor.

I'm running the latest version of Mountain Lion. I am using the ATI Radeon HD 5770. The card has two mini display ports and one DVI port. On the two min DP ports I have active DVI converters to my normal monitors. The third DVI port I have connected to the TV with a DVI -> VGA cord.

The HDTV comes up fine but at a resolution of 1360x768. I know that VGA can do 1920x1080 so I don't understand why it won't work.

I had a spare mini DP -> HDMI cable that I then tried on the HDTV and that made it display in 720p. It also killed my 3 monitor setup due to the active converters. (I started to wonder if the TV could do 1080p at all. Plugged in my PS3 and it came up 1080p.)

So I don't know what else to try. I considered trying a DVI -> HDMI converter as a last resort. Any other ideas or tricks to make my Mac output 1080p to this HDTV?
Click to expand...

VGA is analog

It seems that there is no EDID info getting to the card

SwitchResX might work as a Band Aid to force the resolution, but it woul;d be better to find a way to send digital signal to the TV. DVI would be good, or HDMI.
 
poisoncoyote said:
I am using the DVI port on my card for the HDTV. The Mini DP ports are working fine with my original monitors. I have the correct "active" adapters so that I can run three monitors. I'm still just not getting the right resolution out of the DVI port to the HDTV.
Click to expand...

Perhaps you could try a DVI to HDMI cable?
 
Just tried the DVI -> HDMI converter along with an HDMI cable. No deal. The HDTV shows up as 720p.

*edit - Using the HDMI port, the displays options now allowed me to select 1080p from the scaled options. It would not allow me to select that with the VGA.

Thanks for everybody's help.
 
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