Running 3 displays on a Mac Pro with a single ATI Radeon HD 5770?

Question

Hi all,
I am trying to run 2 19" widescreen monitors with VGA connections and a Sony 32" tv simulantaneously on my Mac Pro. Was wondering if anyone could offer some knowledge on this highly discussed topic...As far as I am aware the main problems that seem to arise with other users on similar forums when trying to do this is the mis-informed use of passive adapters as opposed to active adapters. Is this correct, or is there more to consider here? Do I need to buy a second HD 5770?
After some research here is my proposed setup:
Monitor 1: ACTIVE mini displayport to VGA adapter
Monitor 2: ACTIVE mini displayport to VGA adapter
Monitor 3: DVI port to HDMI cable
Should this solve my problems?
The active adapter that I am looking to buy is this:
http://www.accellcables.com/products/DisplayPort/DP/mdp_vga.htm    
Hope someone out there can be of some assistance,
Thanks,
Stefan.

Answer 1

That setup should work.  I believe all mini-displayport (mDP) to vga adaptors are considered as "active".  I know that apple documents that their adaptor is considered active (see note in this doc).  So you satisfy the requirement of having two active adaptors to support three monitors on a 5x70.  And I think the Accell one you linked to is also fine.
Note, that while your setup will work to drive the video to the two vga's and HDTV's, you still need to address how to pass audio to the HDTV.  DVI does not support audio.  If you aren't interested in passing audio then you can ignore the reast of this post.
In my setup with a 5870 I have a vga monitor going through one of the apple mDP-to-vga adaptors (that counts as one active adaptor).  I also have a 2010 27" apple LCD monitor which of course connects directly to the second mDP (no active adapter so I still need a another).  And like you I want may HDTV connected to the DVI.  So to satisfy the requirement of a second active adaptor, and to also avoid having to pass analog audio cables to the TV (which you have the option to do with your setup), I chose to use the following device with satisfies the requirement of an "active" adaptor.
DVI & S/PDIF Digital Coax/Optical Toslink Audio to HDMI Converter
This allows me to pass the DVI and TOSLINK (digital) audio to that converter and string a single HDMI cable to my HDTV.  Works perfectly.  The only thing about that converter is it's limited to 1080i, not 1080p.  I don't care, couldn't tell the difference anyway on a 32" HDTV.
Finally, to go along with all this I use SwitchResX which allows me to set up multiple monitor configurations.  So I can enable the TV when I want to use it from my computer and disable it when I don't.  And I can switch the configurations with a menu or hot-keys.  And with a little applescripting which you can add to SwithResX configurations I can even switch the audio from my computer to the TOSLINK, i.e., switch between my computer speakers and those attached to the TV.