If you have three displays connected to each graphics card in one of the following configurations:
- a Mac Pro (Mid 2010) or Mac Pro (Mid 2012) that has either the ATI Radeon HD 5770 or ATI Radeon HD 5870 graphics upgrade kit
- two ATI Radeon HD 5770 graphics cards
- a Mac Pro (Early 2009) that has a ATI Radeon HD 5870 graphics card
... you might see one of the following issues:
- When using a DVI connection and two HDMI displays, the display connected using DVI might not have video.
- When using a DVI connection, a Mini DisplayPort, and an HDMI connection, the display connected using DVI might not have video.
- When using a DVI connection and a HDMI connection, adding an additional HDMI connection or a Mini DisplayPort connection might cause the initially-connected HDMI device to no longer appear in the Graphics tab of System Profiler.
If you use three displays with an ATI Radeon HD 5770 or ATI Radeon HD 5870 card, you should use only one DVI or HDMI device.
The Mini DisplayPort to DVI Adapter (different from the Apple Mini DisplayPort to Dual-Link DVI adapter) is considered a single-link, passive DisplayPort device. However, you should use only dual-link adapters (also known as "active DisplayPort" adapters) with multiple display configurations. Single-link DVI to Mini DisplayPort (or VGA) adapters may not work as expected in multiple display configurations.
If you use three displays, you should connect at least two of them with a Mini DisplayPort. You can also use the Apple Mini DisplayPort to Dual-Link DVI adapter or the Apple Mini DisplayPort to VGA adapter or just connect the devices to the graphics card using their native Mini DisplayPort connectors.
The Apple Mini DisplayPort to Dual-Link DVI adapter and Apple Mini DisplayPort to VGA adapter are considered active adapters.
Display adapters (whether they're made by Apple or a another manufacturer) should be connected directly to the display and the video card. You should not "daisy chain" or otherwise connect a secondary video adapter to them.
Learn more about supported display configurations for the Mac Pro.