Planned connection option with this cable:
SAPPHIRE TECHNOLOGY Radeon HD 6870-1 GB GDDR5 - PCI-Express 2.1 (11179-09-20G) - HDMI out
Dell UltraSharp U2412M 61 cm (24 inch) LED monitor (DVI, VGA, 8ms response time) - DisplayPort in
Monitor DisplayPort input do not, at least with this cable - Unfortunately, this variant GraKa HDMI output works. Conversely (DP out - in HDMI) cable seems to be working, according to the good reviews but properly - so a "one-way street".
Well: Learning by doing. But if I interpret the results of my Internet search properly seems HDMI-out after DP-in without an active component in principle not be possible.
There are active converter that can something (eg here:. Ligawo ® HDMI Converter to DisplayPort adapter), the price was too high but for me. Therefore, I have no experience, such converters in practice how good or bad.