Cintiq 24HD as third monitor

Supposedly the HD5770 is powerful enough to support these three monitors

Well not quite. Read these:

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

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

Basically two of the connections need active adapters to supply the additional power. It's up to you to juggle your various connections and what active and possibly passive adapter combinations you want to use for the three connections.

What kind of connection does that Cintiq 24HD want?

Never mind. Found the specs for that Cintiq 24HD. The key items are it wants DisplayPort, DVI, or VGA and has a max resolution of 1,920 x 1,200.

So, thinking out loud, the possibilities are you need to get active adapters for one remaining mini-displayport (mDP's) and the DVI port since I would consider the mDP to the 27" out of the running and not to be touched. The two "players" in this are your HDMI monitor and the Cintiq.

So before proceding further I would need to know how do you desire the Cintiq to be connected? Would its VGA be sufficient or do you want DVI or Displayport?

If it has a DisplayPort input, why not use a Mini DisplayPort to DisplayPort adapter or cable to run the Cintiq?

That drops the number of "legacy" displays to two, and then there is enough power to run them without having to switch up to the expensive USB-powered adapters.

At the moment he has a (passive) mDP-to-HDMI tying up his one remaining mDP. The Cintiq can use displayport or DVI or VGA. But I think no matter how these two displays are connected somehow the requirement of two active adapters needs to be satisfied somehow. I think he already tried directly connecting all three and it didn't work.

Thinking out loud again...

If VGA is chosen for the Cintiq then of course connecting a mDP-to-VGA adapter (well, at least apple's) counts as one active adapter. Then an active adapter would need to be found for the active DVI-to-HDMI connection. Last time I looked that was problematic (or expensive). Would just using the single VGA adapter work? I don't know.

An active mDP-to-HDMI might work for the HDMI (one from the "AMD Eyefinity Validated Dongles" table). Is that sufficient to allow the Cintiq to directly connect to the DVI port? Again I don't know. But probably adding another one of those adapters from the "AMD Eyefinity Validated Dongles" table would be sufficient.

If the HDMI connection was to a TV I wouldn't hesitate to recommend what I've recommended in similar posts, i.e., active mDP adapter for a monitor and the (active) DVI/SPDIF converter box for the DVI port. But that's not the case here. It would work here, ignoring the audio, but it seems like a bit of a waste.

The "AMD Eyefinity Validated Dongles" table doesn't show any active HDMI adapters. I said that was problematic above. I also said I don't know if you could get away with only using a single active adapter. You may just have to do that experiment.

A couple of choices are the following:

DVI-D Single Link Male to HDMI® Female adapter

Passive adapter to plug you HDMI into your DVI port.

Accell B087B-006B UltraAV Mini DisplayPort to DVI-D Single-Link Active Adapter

This is on the Eyefinity table an is a active adapter to connect your Cintiq to your mDP. And looking at the picture of the Accell it is a male DVI plug so I think you also need a DVI coupler (gender changer) since I assume your Cintiq has a male DVI plug.

DVI Coupler (Female to Female)

As I said this is only considered an "experiment" since only one active adapter is being used. At least it would answer the question about whether there's enough power with this setup. If not then you need to figure out how to handle that DVI-to-HDMI connection with some kind of active adapter.

You should be able to see what's going on here. It's sort of a a big "game". You think up one set of requirments. Do a whole lot of google searches to find out what's out there and if you can't find stuff to satisfy that set of requirements, think up some other set of alternatives, and try, try, again.

This was the technique I used and how I originally stumbled upon that DVI/SPDIF converter box. I've since discovered that box is sold by a lot of online sources. The only difference is each slaps a different decal on the top!

Note that given the setup I just descibed, if the single Accell B087B-006B isn't sufficient you may just have to consider that box since it will count as an active adapter for the HDMI connection. It does for me (I use it for my TV), with my other "active" adapter being a (apple) mDP-to-VGA adapter to a 17" VGA monitor. Other mDP is of course connected to my 27" ACD.

Good luck and happy hunting 😉

Hi X423424X and PhineDesign,

I wanted to ask if you guys found a solution to your problem (Its been a year I know 😝)
I want to ask if a Mackbook pro 15 with thunderbolt port can be simultaneously connected to a Apple 27" Cinema Display and a Wacom Cintique 24HD while keeping the MacBook's display on as well....

I just couldn't find an answer to this anywhere Please help 😟

Did you ever find a solution? I'm having the same exact problem except with a Cintiq 13HD (HDMI port). I have the same GPU as you, same amount of ports..

Two Dell 24" LEDs hooked up.

1 mDP to DVI adapter

1 directly to DVI

Cintiq hooked up mDP to HDMI adapter

No such luck. Only two power at the same time when all 3 are plugged in. If I unplug one of the monitors, the Cintiq powers on, just like yours.

Would love to know how you ended up solving your problem! 🙂

The Cintiq 24HD has a DisplayPort input. Connect this device with a Mini DisplayPort to DisplayPort cable, and you will get faster better graphics and solve this "Legacy" adapter problem.

There are no active components in such as cable -- it is "all wires", no conversions. Available for under US$10.