In base alle specifiche Apple elencate sotto Specifiche tecniche per Mac Pro dovrebbe essere in grado di gestire 3 display a fino a 2560 by 1600 pixels
sulle connessioni digitali. Penso che il problema derivi da un po 'di tecnologia conosciuta da AMD, chiamata Eyefinity . Che sembra richiedere adattatori "attivi" per poter eseguire più di 2 schermi alla volta.
Secondo AMD che fa la scheda 5770 ATI.
What are the basic requirements for connecting multiple displays?
Connecting multiple monitors for AMD Eyefinity technology couldn’t be simpler. There are four easy rules to remember:
The first two monitors can connect to the graphics card with any display output on your product: HDMI, VGA, DVI or DisplayPort.
The third (or greater) display must be connected to the graphics card via DisplayPort.
If your monitor does not have a DisplayPort connection, you will need an inexpensive active DisplayPort adapter for it. DVI to DP adapters can be had for less than $30 USD.2
Every family of GPUs supports a different maximum number of displays.
Sembra che tu possa avere gli adattatori passivi per gli adattatori da MiniDP a DVI. e quindi il problema e perché solo 2 display funzionano quando tutto DVI. Nota che il MiniDP a VGA sono adattatori attivi.
Con la risoluzione 1920 X 1200 starai bene con gli adattatori Single Link, hai solo bisogno di una porta mini display attiva per gli adattatori DVI. Per ulteriori informazioni su come ottenere gli adattatori compatibili, consulta AMD Validated Dongles
Come indicato in una domanda simile su Apple Store :
Q:To use three monitors, does this work with the recently-available active single-link DP to DVI adapters (NOT the simple passive one that Apple [sold])?
Late last year, active single-link DVI adapters became available that function in the same way as the active dual-link adapter that Apple sells, but is intended for use with smaller, single-link monitors. These provide the same added intelligence that the dual-link adapters provide, but only support single-link resolutions. This makes them much cheaper (typically around $30) and they don't don't require the extra power of a USB port.
Can these adapters be used with this card in a mid-2010 (5,1) Mac Pro to drive the second and third monitors in a three-monitor setup?
Answer: To run 3 monitors with this card - 2 of them need to be "active" on the display port connections.
I run the card with 2 display port monitors (an HP and DELL) and 1 DVI monitor - (A 1080p projector with an hdmi/dvi passive adapter). I'm doing this in both a 2010 and 2008 mac pro.
I assume because of this, you can buy the active dual-link dvi/dp adapter and get the same results.
But I can confirm you can't do this with a passive adapter.