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User profile for user: Logicalways
Logicalways Author
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ATi 5870 Can only Display 2 out of 3 monitors

Hey Guys!


My ATi 5870 can only display 2 out of 3 ports at a time, it takes the first 2 connections and then drops the 3rd one. So I know the ports work because I can get a single monitor to work in one of the 3 ports no problem. It all started when I replaced my 24" Cinema Display and switched it for an Asus PA248Q. I've had all 3 Original monitors working for 3 years, then I took out the Cinema Display and put in the Asus and everything went bonkers. Here's what I have now:


2009 MacPro 8core 4,1

ATi 5870

2x HP L2445 Monitors (Original)

1x Asus PA248Q (Just added)

All running at 1920x1200 @ 60hz


The cables I have to play with are:

1x Dual-Link DVI to MiniDisplay Port Adaptor

1x HDMI To MiniDisplay Port Adaptor

1x Dvi-D to MiniDisplay Port Adaptor


I never touched the HP monitors (which are my left and right screens) when i put in the new Asus in the middle. They stayed connected to the DVI port and the Dual-Link to MiniDisplay Port adaptor. They worked fine. Then I didn't want to buy a 2nd Dual-Link Adaptor for $120 so I used my HDMI to MiniDisplay Port adaptor I have for my MacBook Air. The HDMI adaptor worked fine to my surprise, but the Dual-Link Adaptor for my HP stopped working.


I Switched out each cable, tried plugging in the Asus to the Dual-Link DVI adaptor instead of the HDMI and trying a bunch of different options, and yet, I can only get 2 of the 3 monitors to turn on with priority to the first 2 plugged in.


My thought is for some reason the ATi card doesn't have enough power but that doesn't really make to me, but i'm not a super technical person in that aspect.

Also, once or twice an hour, the Asus monitor (Via HDMI to MDPort) cuts out and back in again... weird...


Any thoughts that help get these monitors working in tandem would be much appreciated.



Cheers

Posted on Mar 6, 2014 2:52 PM

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
127,201 points

Posted on Mar 6, 2014 3:16 PM

If any of those displays has a DisplayPort or Mini DisplayPort connector, switch over to that. The cables are cheap and provide full resolution with no hassles.


The issue IS, in fact power. AMD says there is not enough to run three "legacy" displays (i.e., not [Mini] DisplayPort), unless all adapters are ACTIVE [read: powered] .


But if you do not need another Dual-Link, you should get by with an ACTIVE Mini DisplayPort to Single-Link DVI adapter, about US$30 from StarTech or Accell (use extreme caution in choosing ACTIVE and Mini DispayPort, as they make all combinations).

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
127,201 points

Mar 6, 2014 3:16 PM in response to Logicalways

If any of those displays has a DisplayPort or Mini DisplayPort connector, switch over to that. The cables are cheap and provide full resolution with no hassles.


The issue IS, in fact power. AMD says there is not enough to run three "legacy" displays (i.e., not [Mini] DisplayPort), unless all adapters are ACTIVE [read: powered] .


But if you do not need another Dual-Link, you should get by with an ACTIVE Mini DisplayPort to Single-Link DVI adapter, about US$30 from StarTech or Accell (use extreme caution in choosing ACTIVE and Mini DispayPort, as they make all combinations).

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User profile for user: Logicalways
Logicalways Author
User level: Level 1
0 points

Mar 6, 2014 3:32 PM in response to Grant Bennet-Alder

Thanks Grant, Power is what I was thinking the problem looked like. I'm not sure what the term "Legacy" Displays is but I'm currently using the Apple Active Dual-Link DVI adaptor though, and one Dual Link DVI plugged directly into the DVI port as the card has 2 MDPorts and 1 DVI Port. I thought using the Active Dual-Link Adaptor would help with the power issue and treat it similar to using my old cinema display which was, i'm guessing, self powered?


- The Asus PA248Q has HDMI, Display Port, DVI and D-Sub VGA on the back.

- The HP L2445m has DVI or D-Sub VGA


I think even with a second Active Dual-Link Adaptor it may not work...


Does anyone think that 2x Active Dual-Link DVI to MiniDisplay Port Adators + Straiight DVI will help the ATi 5870 to run 3 monitors? Or am I wasting my money buying a cable that wont work?

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ATi 5870 Can only Display 2 out of 3 monitors

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