Three displays with ATI Radeon HD 5870 Mac Pro Early 2008

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Three displays with ATI Radeon HD 5870 Mac Pro Early 2008

So I've found a few threads and a couple of Apple support docs about this, but I'm still a bit hazy on what to do and don't want to spend any more $ while experimenting, so I figured I'd come to the board.

I have a Mac Pro (Early 2008) with an ATI Radeon HD 5870 graphics card. It has two Mini Display ports and one Dual Link DVI port.

I'd like to be able to run three displays simultaneously. Two are standard computer monitors (Acer and Dell), and one is a Toshibia 50" HDTV. I can always get two to work, but never three.

My current configuration is:

1. a Mini Displayport to HDMI cable > the Toshiba HDTV (direct connection)

2. a Mini Displayport to Single Link Active DVI adapter > DVI cable > the Acer

3. a Dual Link DVI cable > the Dell (direct connection)

This support doc tells me that to do this, I just need to run cables directly from the card ports to the displays themselves.

So the mistake I'm making is with #2, and what I need is to duplicate #1, that is a Mini Displayport to HDMI cable directly to the Acer (it can accept HDMI)

However, this thread and this thread seem to say that the Mini Displayports need ACTIVE adapters because there is not enough power behind them.

If this is my problem, then the mistake I'm making is with #1, and I need an Active Mini Displayport to HDMI adapter going to the Toshiba.

Of course, it's possible that I'm not understanding the power issue, and that really either solution would work, but would be great to know so I can decide between the two.

Then there is this Apple support doc, which means neither option will work and I'd need to throw a VGA cable into the mix.

Posted on Jul 13, 2015 12:29 PM

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Answer 1

Jul 13, 2015 12:35 PM in response to naveenmedia

[two are] standard computer monitors, one is HDMI

The notion of what is "standard" has changed. According to the manufacturer of that card, "standard" is DisplayPort or Mini DisplayPort. Anything older is "legacy".

"In order to run more than TWO "legacy" displays, you need to be using ACTIVE adapters beyond the first two."

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Answer 2

lllaass

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Jul 13, 2015 12:44 PM in response to Grant Bennet-Alder

It should work since you say you are using one active adopter

2. a Mini Displayport to Single Link Active DVI adapter > DVI cable > the Acer

Just what active adopter is it? Do you have a link for the adopter?

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Answer 3

Jul 13, 2015 10:29 PM in response to naveenmedia

Both Mini DisplayPort adapters must be Active if you are using three displays.

<http://www.startech.com/AV/Displayport-Converters/Mini-DisplayPort-to-HDMI-Activ e-Video-and-Audio-Adapter-Converter-Mini-DP-to-HDMI-1920x1200~MDP2HDS>

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Answer 4

lllaass

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210,513 points

Jul 14, 2015 1:32 AM in response to Malcolm J. Rayfield

To my knowledge if you have three legacy connections only one has to be active.

What leads you to believe tat two have to be active?

Malcolm J. Rayfield wrote:

Both Mini DisplayPort adapters must be Active if you are using three displays.

<http://www.startech.com/AV/Displayport-Converters/Mini-DisplayPort-to-HDMI-Activ e-Video-and-Audio-Adapter-Converter-Mini-DP-to-HDMI-1920x1200~MDP2HDS>

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Answer 5

Jul 14, 2015 2:55 AM in response to lllaass

lllaass wrote:

To my knowledge if you have three legacy connections only one has to be active.

That's true for the new Mac Pro (2013), but not for the older three port graphics cards..

What leads you to believe that two have to be active?

<https://support.apple.com/HT203389>

<https://support.apple.com/HT202090>

Note that these Apple articles only mention Apple adapters, and the only active Apple adapters are VGA and Dual-Link DVI. There are non-Apple HDMI and Single-Link DVI adapters.

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Answer 6

naveenmedia Author

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Jul 14, 2015 8:12 AM in response to Grant Bennet-Alder

The notion of what is "standard" has changed. According to the manufacturer of that card, "standard" is DisplayPort or Mini DisplayPort. Anything older is "legacy".

Got it. So both my computer monitors would be considered legacy. I suppose the TV is as well, since it doesn't take Displayport or Mini Displayport? (Or does that only apply to computer monitors).

In any case, that leads me to connecting the Dell to the Dual-Link DVI port on the card. I'm hoping that is ok (direct connection via DVI cable) and that I don't need an adapter, only for the Mini Displayports?

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Answer 7

naveenmedia Author

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Jul 14, 2015 8:14 AM in response to lllaass

lllaass wrote:

Just what active adopter is it? Do you have a link for the adopter?

This is adapter I'm using: http://www.amazon.com/Accell-B087B-006B-DisplayPort-Single-Link-Certified/dp/B00 4071ZXA

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Answer 8

lllaass

Level 10

210,513 points

Jul 14, 2015 8:27 AM in response to Malcolm J. Rayfield

The only active adopter discussed by those two Apple article are the MDP>VGA and dual-link adopter. Apple does not make an active single-link DVI adopter. Thus, those do not say that a single-link active adopter will not work for resolutions <19020X1200.

Malcolm J. Rayfield wrote:

lllaass wrote:

To my knowledge if you have three legacy connections only one has to be active.

That's true for the new Mac Pro (2013), but not for the older three port graphics cards..

What leads you to believe that two have to be active?

<https://support.apple.com/HT203389>

<https://support.apple.com/HT202090>

Note that these Apple articles only mention Apple adapters, and the only active Apple adapters are VGA and Dual-Link DVI. There are non-Apple HDMI and Single-Link DVI adapters.

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Answer 9

lllaass

Level 10

210,513 points

Jul 14, 2015 8:28 AM in response to naveenmedia

Maybe it is a bad ACTIVE adopter

naveenmedia wrote:

lllaass wrote:

Just what active adopter is it? Do you have a link for the adopter?

This is adapter I'm using: http://www.amazon.com/Accell-B087B-006B-DisplayPort-Single-Link-Certified/dp/B00 4071ZXA

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