I just read on Wikipedia about the compatibility for HDMI/DVI/VGA
Maybe this article helps understanding your problem
-----------------------------------
Copied from Wikipedia
Dual-mode DisplayPort (also known as DisplayPort++[26]) can directly emit single-link HDMI and DVI signals using a simple passive adapter that adjusts for the lower voltages required by DisplayPort.[3][27] When dual-mode chipset detects that a DVI or HDMI passive adapter is attached, it switches to DVI/HDMI mode which uses the 4-lane main DisplayPort link and the AUX channel link to transmit 3 TMDS signals, a clock signal and Display Data Channel data/clock. Dual-mode ports are marked with the DP++ logo; most current DisplayPort graphics cards and monitors offer this mode.
A notable limitation is that dual-mode can only transmit single-link DVI/HDMI, as the number of pins in the DisplayPort connector is insufficient for dual-link connections; an active converter is needed for Dual-Link DVI (and analog component video such as VGA, since it employs digital to analog conversion). Active conversion can be powered by +3.3 V wire in the DisplayPort connector, but some active adapters require external power.[28]
VESA foresees that all HDMI and DVI conversion will eventually be handled by active adapters which act as DisplayPort Sink devices, in order to facilitate easier updates to latest HDMI and DisplayPort specs, and work with dual-link HDMI, DisplayPort connections with either fewer than 4 lanes or different data rates, and multiple DisplayPort streams. It should be noted that DVI 1.0 spec was finalized in 1999 and the DVI industry consortium has since disbanded, so future updates to DVI specification are unlikely; also, although dual-link HDMI Type B connector is defined in the HDMI specification, it has not seen any practical use as of 2012.
-----------------------------------
Try the Displayport to DVI adapter, it does not cost much. In our company we use many of these adapters and theyre all working for LCD's.
Maybe this article helps understanding your problem
-----------------------------------
Copied from Wikipedia
Dual-mode DisplayPort (also known as DisplayPort++[26]) can directly emit single-link HDMI and DVI signals using a simple passive adapter that adjusts for the lower voltages required by DisplayPort.[3][27] When dual-mode chipset detects that a DVI or HDMI passive adapter is attached, it switches to DVI/HDMI mode which uses the 4-lane main DisplayPort link and the AUX channel link to transmit 3 TMDS signals, a clock signal and Display Data Channel data/clock. Dual-mode ports are marked with the DP++ logo; most current DisplayPort graphics cards and monitors offer this mode.
A notable limitation is that dual-mode can only transmit single-link DVI/HDMI, as the number of pins in the DisplayPort connector is insufficient for dual-link connections; an active converter is needed for Dual-Link DVI (and analog component video such as VGA, since it employs digital to analog conversion). Active conversion can be powered by +3.3 V wire in the DisplayPort connector, but some active adapters require external power.[28]
VESA foresees that all HDMI and DVI conversion will eventually be handled by active adapters which act as DisplayPort Sink devices, in order to facilitate easier updates to latest HDMI and DisplayPort specs, and work with dual-link HDMI, DisplayPort connections with either fewer than 4 lanes or different data rates, and multiple DisplayPort streams. It should be noted that DVI 1.0 spec was finalized in 1999 and the DVI industry consortium has since disbanded, so future updates to DVI specification are unlikely; also, although dual-link HDMI Type B connector is defined in the HDMI specification, it has not seen any practical use as of 2012.
-----------------------------------
Try the Displayport to DVI adapter, it does not cost much. In our company we use many of these adapters and theyre all working for LCD's.