I am a little confused as to what the issue is, but I wanted to provide an additional data point. My config seems to be working fine.
I have the 8-core 2.4ghz, 5770
1. DVI port, 30" dell (dual link dvi, no adapters used)
2. mini-displayport 1, mini-display port to displayport 10' cable into 24" dell display
3. mini-displayport 2, mini-display port to displayport 10' cable into 27" dell display running at a dual-link resolution, no adapters
This config works just fine.
i can just attach this I guess, a lot of detail
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:
DELL 2408WFP:
Resolution: 1200 x 1920 @ 60 Hz
Pixel Depth: 32-Bit Color (ARGB8888)
Mirror: Off
Online: Yes
Rotation: 90
Connection Type: DisplayPort
DELL U2711:
Resolution: 2560 x 1440 @ 60 Hz
Pixel Depth: 32-Bit Color (ARGB8888)
Mirror: Off
Online: Yes
Rotation: Supported
Connection Type: DisplayPort
Television: Yes
DELL3007WFPHC:
Resolution: 2560 x 1600
Pixel Depth: 32-Bit Color (ARGB8888)
Main Display: Yes
Mirror: Off
Online: Yes
Rotation: Supported