I have a custom home theater PC setup with the TV (a Sharp LCD) connected as monitor 3 via HDMI to my Windows 7 PC. I use an ATI/AMD 6770 graphics card with support for 3 monitors... I have two touchscreen monitors connected (via DVI and a second HDMI port) to the same card. Windows is configured to span the desktop over all 3 displays.
When I power on the TV the display on both monitor 1 and monitor 2 goes black for a couple of seconds. We'll call this blackout 1. Then it comes back for a few seconds (presumably as the TV warms up), and then goes black again (blackout 2) for a few more seconds. Everything is fine after that.
I believe blackout 1 is caused by the hardware on the graphics card detecting a new signal and reconfiguring resources internally. I believe blackout 2 is caused by Windows detecting a new display as reported by the graphics drivers and reconfiguring the Windows desktop. I don't have evidence of this, but it makes logical sense.
How can I eliminate one or both of these blackout periods?
The two touchscreen monitors are control interfaces for the HTPC. It is incredibly annoying to have the entire HTPC UI go black not once but twice whenever the TV is powered on. I am open to any suggestions, including using a separate graphics card for the TV or not spanning the desktop or even switching to NVidia hardware if that might make a difference.
I should clarify that I think both the graphics card and Windows are working as intended: these blackouts are probably fine in most environments. My particular scenario however really depends on no interruption in the video feed to the two touchscreens.