Here is a look at the inside of the STX-HD100, as viewed from the rear, and above, the unit. As you can see, just as in the previous photo, there is plenty of open space.
The left side of the photo shows the power supply board. You can see where the board connected to the Master Power Switch and the AC Cord. This board provides and regulates all the needed power used by the processing board.
On the right side is network, audio, and video processing board, and if you look closely, you can see where the rear panel outputs actually connect to the board.
By the same token, you can see the several processing chips that are devoted to various operations of the STX-HD100.