Radeon 5870 - Only 2 displays at a time??

slughead

macrumors 68040
Original poster
Apr 28, 2004
3,104
236
I have 2 DVI monitors, an HDMI TV, an Apple brand Mini-display port to DVI adapter, and a 3rd party MDPort to HDMI adapter.

Only a combination of TWO will work at once: both DVI monitors (one through the MDPort w/adapter), one of the DVI monitors through the MDPort + the HDMI TV, one of the monitors through the DVI port + HDMI TV. The 3rd display is always black.

The DVI monitors are indentical-modeled Samsung 22" monitors (not dual link), the TV is 720p.

Let me be clear: the 2 displays that do work, work PERFECTLY, whether it be the TV or the Samsung monitor. Even the HDMI audio works absolutely perfectly. I can plug in the 3rd display and that will work perfectly too as long as I unplug one of the others.

I read a troubleshooting article whose solution was basically "yeah, don't use 3 monitors, derp"... Not what I bought this machine to do.
 

slughead

macrumors 68040
Original poster
Apr 28, 2004
3,104
236
Alright, so I read a little about active Vs Passive and did a TON of googling. Here is what I found:

This is a problem with the ATI cards themselves, not just Apple.

It appears that the whole Active MDP -> DVI thing is pretty cheap and easy, but HDMI is more difficult.

I love my HDMI audio and I'm not giving it up by using an Active MDP -> DVI then DVI -> HDMI. This puts me in a bind because there appear to be NO active MDP or DisplayPort -> HDMI adapters for sale at any price.

I have a spare 4870... the problem is powering it with the 5870 in the case already. I just got this damn computer and already I'm rigging it to be as ridiculous as my last one.
 
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marcng

macrumors newbie
Jun 9, 2009
29
0
my Moshi MDP-HDMI adaptor passes audio through with no problem.
not sure if this is what you want.

http://www.moshimonde.com/productDetail.aspx?group=19

Alright, so I read a little about active Vs Passive and did a TON of googling. Here is what I found:

This is a problem with the ATI cards themselves, not just Apple.

It appears that the whole Active MDP -> DVI thing is pretty cheap and easy, but HDMI is more difficult.

I love my HDMI audio and I'm not giving it up by using an Active MDP -> DVI then DVI -> HDMI. This puts me in a bind because there appear to be NO active MDP or DisplayPort -> HDMI adapters for sale at any price.

I have a spare 4870... the problem is powering it with the 5870 in the case already. I just got this damn computer and already I'm rigging it to be as ridiculous as my last one.
 
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initialsBB

macrumors 6502a
Oct 18, 2010
688
2
As alphaod says, keep your HDMI as a passive connection. When I researched this a while back I understood that only the third connection had to be active, the other two can stay passive and it should work.


OT Why is it that every time I click on an Apple KB article link I get a 404 error ? If I copy and paste the link it works.
 
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alphaod

macrumors Core
Feb 9, 2008
22,167
1,212
NYC
I love my HDMI audio and I'm not giving it up by using an Active MDP -> DVI then DVI -> HDMI. This puts me in a bind because there appear to be NO active MDP or DisplayPort -> HDMI adapters for sale at any price.
That's why I said to use a DVI to HDMI adapter and hook up your DVI monitors to miniDisplayPort via active adapters.
 
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slughead

macrumors 68040
Original poster
Apr 28, 2004
3,104
236
As alphaod says, keep your HDMI as a passive connection. When I researched this a while back I understood that only the third connection had to be active, the other two can stay passive and it should work.
That's not accurate, both MDP adapters have to be active to get 3 displays working, according to numerous articles including Apple's. Sapphire has an ATI card (6000 series??) that only requires 1 active adapter, but I have the stock Apple 5870 :(

That's why I said to use a DVI to HDMI adapter and hook up your DVI monitors to miniDisplayPort via active adapters.
Yes I understand that, and it's a good thought.The problem is DVI has no audio, so doing DVI -> HDMI would effectively leave me with a video-only connection which is not acceptable unfortunately (GF hates my little speakers, wants to use TV's output).
 
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ActionableMango

macrumors G3
Sep 21, 2010
9,510
6,750
Yes I understand that, and it's a good thought.The problem is DVI has no audio, so doing DVI -> HDMI would effectively leave me with a video-only connection which is not acceptable unfortunately (GF hates my little speakers, wants to use TV's output).
Run a separate audio cord to the TV.
 
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slughead

macrumors 68040
Original poster
Apr 28, 2004
3,104
236
I've decided to add another PSU and throw in my old 4870 to drive the extra monitor. I have the PSU, I have the card, I might as well use it (though not very elegant, it'll do the job).

Thanks for your help, everyone!
 
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