three monitors, early 2008 Mac Pro?

Hello there, awaking an old thread. I need help getting my 3rd monitor up and running off of my Radeon 5770 in my early 2008 Mac Pro 3.1. The original video card went dead a few months ago so I got the 5770 in hopes of having 3 monitors in my recording studio. Well, not so fast...

Here's what's going on: My main, center monitor is a large Vizio Razor M series 65" TV. Great TV, and I'm using a MiniDisplay port-to-HDMI adapter to drive this one. Resolution is 1080p in the "scaled" list. That's all it says in the Display window for this one.

The second display is my trusty Apple Cinema HD 30" display, had it for years. This one has built-in Dual-Link support, so it's connected to the sole DVI output on the 5770, along with its USB and Firewire connections. Its resolution is 1920 x 1200

Having these 2 work is no problem. When I attempt to add a third monitor is when things get frustrating. I've got an HP 2311xi monitor connected to the 5770's final MDP outlet via the Apple MDP to Dual-Link DVI adapter. I do have the USB connector plugged into a live USB port. I am then driving the HP monitor using an adapter to convert to an HDMI cable. It's resolution is also shown as 1080p in the "scaled" list. When I plug in the HDMI cable to the HP, the Apple Cinema HD goes black. When I pull the HP HDMI cable back out, the Apple Cinema HD again comes alive.

As I have come to understand, 2 key things must be true: 1) 2 of the 3 ports must have Dual-link DVI connections, and 2) no screen can have more than 1920 resolution. If I'm not mistaken, I meet both those requirements, but I can't seem to get 3 monitors going simultaneously.

One twist. My HP also has a DVI input, so, I also tried a DVI to DVI cable from the adapter to the HP, same result. Never can get the third to simutaneously work.

Any ideas??

Thanks so much!

Greg in Houston

Your understanding is not quite correct.

There is not enough power behind the Mini DisplayPorts to run two passive [read: just wires] adapters on the 5770 and similar ATI cards.

To proceed using two adapters, you need to have all ACTIVE [read: powered] adapters that have signal re-drivers in them.

Apple sells ONLY their deluxe Dual-Link DVI adapter for US$100. It always works and you never get stuck in the Single-Link vs Dual-Link problem, but it costs too much.

Accel and StartTech sell ACTIVE Single-Link DVI adapters (good for up to 1920 wide) for under US$35 from several outlets including amazon.com.

You can use an ACTIVE adapter to Single-Link DVI, then a "just wires" or cable adapter to HDMI (no additional conversion DVI to HDMI is required in that case).

--------

If you want to pursue this more deeply, this article includes a link to further detail and a list of AMD/ATI approved adapters.

http://support.amd.com/us/eyefinity/Pages/eyefinity-dongles.aspx

As I have come to understand, 2 key things must be true: 1) 2 of the 3 ports must have Dual-link DVI connections, and 2) no screen can have more than 1920 resolution.

Both incorrect. When running three displays, any Mini DisplayPort adapters must be ACTIVE, not passive. They do not need to be dual-link unless using resolutions greater than 1920 x 1200.

There are active single-link DVI and HDMI adapters available (but not from Apple):

<http://support.amd.com/us/eyefinity/Pages/eyefinity-dongles.aspx>

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

The dual-link DVI adapter is needed only for DVI displays with resolutions greater than 1920 x 1200.

The card can run up to three displays with resolutions greater than 1920 x 1200 if no passive Mini DisplayPort adapters are used.

For displays with Mini DisplayPort or DisplayPort, don't use adapters, just cables with appropriate connecters.

For best image, don't scale the resolution. When using a TV for display, the dock and menu may go off the screen due to overscan. See if the TV has a setting for 100%, pixel-to-pixel, 1-to-1, full-screen, etc. If there is no such setting, you may have to use OS X's display system preference settings for under or over-scan.

Thank you Grant and Malcolm. So, sounds like I need a single-link HDMI adapter for both my Vizio TV and HP monitor. Is this correct? (as long as I run 1920x1200 or below). And I can return my brand-new Apple $100 dual-link DVI adapter as well? That's a win for the pocketbook.

What I had at first on the Vizio and HP (and still have on the Vizio) is just a simple MDP-to-HDMI converter/adapter. These are "passive" apparently. You are saying this is not enough, if I want 3 active monitors. The Apple Cinema HD Display is correctly connected to the 5770's DVI port (and the USB/Firewire cables into the Mac as well), no other way I see anyway.

Malcolm, regarding the Vizio and it's resolution, it is behaving perfectly currently. The menu bar at top and dock at bottom are placed perfectly; I chose "best for display" on the Vizio as well as the HP monitor.

If you'll confirm this to be correct, I'll set about acquiring the proper bits tomorrow, and return Apple's overpriced adapter as well!

Greg

Correct. All three displays should work with two Active adapters.

Many thanks!

Greg

greg328-

So, sounds like I need a single-link HDMI adapter

I am sure you get it, but for casual Readers who find this by searching, the adapters you need must be advertised as ACTIVE adapters. That means they have the required signal re-driver circuits inside. If it does not say ACTIVE in the description, it won't be -- they are more expensive to make and therefore cost more.

Got it, active it is. I bought a pair of these last night:

http://www.ebay.com/itm/331026126104?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m143 9.l2649

(Visiontek 900636 Mini Displayport To Hdmi Activeadap Active Adapter Cable)

Thanks,

Greg