Somehow my post got sent before I finished writing it.
Here is what I intended to post:
I have a similar problem, but the circumstances suggest a problem with MacOSX 10.7.x.
I have a MacPro model 5,1 with a Radeon HD 5770 card. This machine has 2 hard drives. One (the original) is set up to boot with MacOSX 10.6. The other is set up to boot with MacOSX 10.7.4. I can choose which one to boot from at startup by pressing the option key at the chime.
I needed to be able to view the screen on the TV in the next room, so I got a NewerTech mini displayport to HDMI adapter. This works well, but only under 10.6.
When booted with 10.6, the system profiler shows the following for Graphics/Displays:
ATI Radeon HD 5770:
Chipset Model: ATI Radeon HD 5770
Type: GPU
Bus: PCIe
Slot: Slot-1
PCIe Lane Width: x16
VRAM (Total): 1024 MB
Vendor: ATI (0x1002)
Device ID: 0x68b8
Revision ID: 0x0000
ROM Revision: 113-C0160C-155
EFI Driver Version: 01.00.436
Displays:
SHARP HDMI:
Resolution: 1920 x 1080 @ 60 Hz
Pixel Depth: 32-Bit Color (ARGB8888)
Main Display: Yes
Mirror: On
Mirror Status: Master Mirror
Online: Yes
Rotation: Supported
Interlaced: Yes
Television: Yes
Cinema Display:
Resolution: 1680 x 1050
Pixel Depth: 32-Bit Color (ARGB8888)
Mirror: On
Mirror Status: Hardware Mirror
Online: Yes
Rotation: Supported
Display Connector:
Status: No Display Connected
Note that there are 3 entries under Displays. One of these is an unused mini displayport output.
When booted with 10.7.4, the system profiler shows the following for Graphics/Displays:
ATI Radeon HD 5770:
Chipset Model: ATI Radeon HD 5770
Type: GPU
Bus: PCIe
Slot: Slot-1
PCIe Lane Width: x16
VRAM (Total): 1024 MB
Vendor: ATI (0x1002)
Device ID: 0x68b8
Revision ID: 0x0000
ROM Revision: 113-C0160C-155
EFI Driver Version: 01.00.436
Displays:
Cinema Display:
Resolution: 1680 x 1050
Pixel Depth: 32-Bit Color (ARGB8888)
Main Display: Yes
Mirror: Off
Online: Yes
Rotation: Supported
Note that there is only one entry under Displays. There isn't even any indication that the card has more than one output.
I know that there is nothing wrong with the hardware because I can switch back and forth between the OS's. The mini displayports are recognized in 10.6.8. They are not recognized in 10.7.4.
This looks like a bug in the display driver in 10.7.
Anyone have any ideas how to fix this?
Thanks for any insights.