When I was using a Nvidia GT240 and had my TV on the HDMI output of that card, it never showed any graphics until the login in screen (though it would be black and allow the mouse into that area in the screen or display the login screen depending on if I had selected the TV as the "default display" or not as the case may be).
However, I am now curently using an ATi Radeon HD4670, which displays both on the HDMI and the VGA from the BIOS, then when it detects the SATA drives ( which are in ACHI mode) it shows the results in the TV, then the "Starting Windows" screen is displayed in both screens (VGA and HDMI).
I highly doubt its the TV. I would say its more APU side than mobo; my mobo and TV are the same in both instances. In either case I dont think theres a lot you can do about it except live with it - unless you want to change graphics cards?