Two DVI monitors on new MacPro - workaround?

you use dual link active adapters to use higher resolution monitors.

http://support.apple.com/kb/HT5918

It looks pretty clear to me; three DVI displays is a no-go. The fact that they cover what happens if you hang one on the HDMI port tells me there is probably some sort power issue.

zzyzyman wrote:

@RatVega™: The same problem occurred on the dated 5750 Radeon card; despite 4 connections on it, it only supported a combination of monitors (eg. 1 DisplayPort and 2 DVI). In some cases, this was worked around by using active adapters.

I don't believe a Mac Pro was ever offered with a 5750 board, so I'll assume that is a typo.

The information about the number of useable ports on an ATI Radeon HD 5770 and the circumstances under which they can be used was and still is available if you looked hard enough at Apple, or you could go to ATI and get definitive info and qualified adapter recommendations. I am currently running two 27" 1080p monitors and a 37' 1080p HDTV with my 5770 and there is no "work-around" involved.

I don't believe a 37' 1080p HDTV is actually offered unless you're talking a sporting venue install, so I'll assume you meant 37" ;-)

Yes, 37-inch... my bad. I guess I was exhausted after searching the archives for a Mac Pro equipped with a 5750 board. 😝

My point was that although the info existed, even if Apple did little to make it available. In the current case, I think they're sending a strong message with the bit about trying to hang a HDMI display along with the DVIs.

This made me recall that my Samsung SyncMaster P2770s have both DVI and HDMI interfaces and how neatly they'd closed the door on a third.

Maybe Grant will stop by and lay out the gory details, but I believe the DVI interface (along with now being passé) likes to gobble up current, something that may be problematic in such a small case.

I had problems getting Apple's 5770 to work with multiple DVI monitors on my circa-2006 MacPro 1,1 as this is an unsupported configuration.

That configuration is not recommended:

Mac Pro (Early 2009), Mac Pro (Mid 2010), Mac Pro (Mid 2012): Issues with three displays and multiple DVI, HDMI connections

But it IS supported, if you are willing to use two Dual-Link DVI adapters at US$100 each:

Mac Pro (Early 2009), Mac Pro (Mid 2010), Mac Pro (Mid 2012): Supported display configurations

I guess I just got lucky on my '08 Mac Pro, all I did was buy a pair of Accell B087B-006B UltraAV Mini DisplayPort to DVI-d Single-Link Active Adapters for $29.99 each.

What's your opinion on the original question, Grant?

At the time Apple published the guidelines for the 5770, they had decided that they only needed to supply the Dual-Link Active adapter, since it worked in every situation, even if it was overkill. The marketing department later decided it was a US$100 device, which should have changed the calculus, but since this Apple, it did not.

In the case of the new Cylinder Mac Pro, we may be seeing another case of Apple recommending only the straightforward solutions that work "first time every time". There may be more subtle arrangements with many more footnotes that Readers will discover over time.

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When card-makers invented DisplayPort (and its mini variant) it had several advantages:

• The constant re-draw of the screen, every 60 to 100 times a second, disappears. Instead, the screen is re-drawn only when it changes. This dramatically reduces traffic on the cable most of the time. But it requires a display with a screen buffer.

• the higher Voltages used for DVI could be replaced with lower Voltages and still work fine.

• When required, "compatibility mode" or "Dual Mode" (to DVI) could be invoked by asserting a signal back toward the computer. Then the port would re-time to DVI compatibility mode, and put out the signals needed (close to, but not quite at the higher DVI levels). A power pin (supplied at the port) could be used by an Active Single-Link adapter to boost the signal levels up for ONE Single-link adapter, and maybe the second one on a card in a pinch.

Dual-Link adapters required three more balanced Drivers each, and the power supplied at the port was just not enough. So the adapter uses a USB pigtail to pick up still more power to run more signal boosters.

-- Apple is saying, "Don't run more than two [DVI and HDMI combined] on a Mac Pro cylinder".

It is not clear whether they are saying this because it will not work, or because of the support firestorm it created for them the last time (since it becomes so complicated).

Those interested may want to read the wikipedia article on DisplayPort, which discusses the History. DVI compatibility is covered under the heading "Dual Mode":

http://en.wikipedia.org/wiki/DisplayPort

.

Thanks for sharing that.

Wait, what? That's on the ORDERING Page?

When are they going to update the knowledgebase articles ?? They still have that vague stuff where we were trying to read between the lines!

Okay so here's my situation...

I have a 40" TV (HDMI)

a 24" Dell Monitor (HDMI)

and a 24" Acer monitor (DVI)

How do I make this work with my cylinder? Can I just buy one Apple Minidisplay to Dual Link DVI adapter for the Acer, and use a normal Minidisplay to HDMI for the Dell, and straight up HDMI for the TV?

Or is it when you have any combination of DVI/HDMI devices, you can only use 2 at a time?

So would I then need TWO of the $99 Dual Link DVI adapters, and then yet another converter to go DVI to HDMI for the Dell display?

Or is it when you have any combination of DVI/HDMI devices, you can only use 2 at a time?

Almost. When you have any non-ThunderBolt, non-DisplayPort [incl Mini DisplayPort] devices, at most two of those are supported using "any-old-adapter". To run more requires an ACTIVE adapter.

Apple's ACTIVE Adapter is an industrial-strength Dual-Link DVI-capable adapter that works in every situation. It is an expensive solution, but it always works.

For displays under 1920 wide, which only require Single-link DVI, you can use a less-expensive ACTIVE Single-Link adapter such as those made by Accell or Startech, about US$30. For conversion to HDMI at 1080p or less, MonoPrice sells a comparable ACTIVE adapter at around the same price point.

Sorry - I think I follow. Even minidisplay port would require an adapter for more than 2 minidisplay native displays?

So bottom line - do I need to buy 1 or 2 active adapters for the setup I described?

Thanks so much for the help

You can run up to six ThunderBolt or [Mini] Displayport because they require no Signal conversions to work, and no extra power.

You only need to start counting when you add adapters to convert to what AMD calls "legacy" display protocols. [Great, now I'm an antique.]