I have GTX750TI connected to the HDMI port of my monitor and HD4600 connected to the D-SUB port of the monitor.
What I'm trying to achieve is to see the same thing while switching between HDMI and D-SUB modes.
With Win+P I can switch to "Duplicate" but then the D-SUB shows black screen.
Does duplicate work only if you are using the outputs of one card not two?
My Computer
At a glance
Windows 7 Ultimate x64 SP1i7 4771 3.5Ghz2x8GB DDR3 GEIL EVO LEGGERAPALIT GTX 750 TI StormX Duo
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Custom Build
OS
Windows 7 Ultimate x64 SP1
CPU
i7 4771 3.5Ghz
Motherboard
ASUS B85 Plus
Memory
2x8GB DDR3 GEIL EVO LEGGERA
Graphics Card(s)
PALIT GTX 750 TI StormX Duo
Monitor(s) Displays
Samsung T24D390
Screen Resolution
1920x1080
Hard Drives
Samsung SSD 840 EVO 128GB
2TB Seagate SATA 3
600GB WD Blue SATA 2
Do you have only 1 monitor? If yes, then why are you trying to duplicate the screen? What are you trying to accomplish?
Try duplicating from Screen Resolution window (right click empty desktop area)
My Computer
At a glance
Windows 7 Ultimate x64 SP1AMD Phenom 2 1090T2x8GB Kingston HyperX Fury Black 1600Mhz Unga...MSI GTX 970 Gaming 4G
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Custom Build
OS
Windows 7 Ultimate x64 SP1
CPU
AMD Phenom 2 1090T
Motherboard
Gigabyte GA-890FXA-UD5
Memory
2x8GB Kingston HyperX Fury Black 1600Mhz Unganged
Graphics Card(s)
MSI GTX 970 Gaming 4G
Sound Card
Realtek On-Board HD 7.1 Audio / Logitech G35
Monitor(s) Displays
3xAcer GD245HQ
Screen Resolution
1920x1080
Hard Drives
Samsung 850 Pro 512GB SSD - OS /
WD Caviar Black SATA 3 - 1 TBx2 - Dynamic RAID 0 /
WD Caviar Green SATA 2 - 640GBx2 - Dynamic RAID 0 /
WD Caviar Green SATA 2 - 640GB - Internal Backup /
Seagate Barracude SATA 3 - 3TB - External Backup/ Sync
PSU
HighPower 1000W
Case
Cooler Master HAF 932
Cooling
Noctua NH-D14
Keyboard
Logitech G19
Mouse
Logitech G500
Internet Speed
100/4 Mbit Cable (100GB quota)
Antivirus
ZoneAlarm Extreme Security / MBAM Pro / MBAE Free / SAS Free