Comment 3 for bug 273484

I also have the same problem. I am running intrepid alpha6 64bit, and nvidia driver 177.
Im am using an Asus nvidia EN9500GT PCI-E discrete graphics card. My monitor is a Hanns.G HG281D LCD panel with HDMI and D-SUB inputs.
The graphics card has dvi, hdmi, and d-sub outputs. My monitor only goes to sleep properly when I use the dsub connection. When I connect my monitor to the HDMI or DVI ouputs of the graphics card, the monitor does not go to sleep properly. Instead, the monitor shows a "No Signal Input" message, but I guess it's not a complete loss of signal, because the monitor does not go to sleep. If I disconnect the cable or turn off the computer then the monitor goes to sleep. I have tried "xset dpms force standby/suspend/off" and they all have the same effect (monitor's own "signal loss" message screen, but monitor never actually goes to sleep).

Some interesting points: Using the "nv" driver does not have this problem (sleep works properly over both DVI and HDMI connection).

Using a different discrete graphics card (EVGA nvidia 8400GS) I don't have this problem
with either "nv" or nvidia drivers.

I am not using twinview or xinerama, just a single connection to a single monitor.