I have a new Mac Pro with a single ATI 5770 card installed. It has two mini-display ports, and one DVI port
I have tried the following configurations:
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All 3 DVI connections: This results in one monitor always being black
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2 Mini to 2 VGA and one DVI – This results in the VGA monitors having a max resolution of 1920×1080 but defaulting to 1600×1200 due to the aspect ratio. All monitors have a 1920×1200 resolution, but only the DVI port is giving this resolution
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All 3 VGA with a DVI to VGA converter on the DVI port – Same result as #2. The monitor plugged into the DVI->VGA port has full resolution. The two Mini->VGA are limited to 1920×1080
My question:
Is this even possible without Apple's dual link adapters?
Best Answer
According to Apple's specs listed under Tech Specs for the Mac Pro it should be able to handle 3 displays at up to
2560 by 1600 pixels
over the digital connections. I think the trouble is coming from a little known about techology from AMD called Eyefinity. Which seems to require "Active" Adapters in order to run more than 2 displays at a time.According to AMD who makes the ATI 5770 card.
It looks like you may have the passive adapters for the MiniDP to DVI adapters. and hence the trouble and why only 2 displays work when all DVI. Note that the MiniDP to VGA are active adapters.
With the 1920 X 1200 resoultion you will be fine with Single Link adapters, you just need active mini display port to DVI adapters. For some guidance on obtaining compatible adapters see AMD Eyefinity Validated Dongles
As noted in a similar question in the Apple Store: