8900 for 2TV'S

Hi, i want to watch my new 8900 on two tv's. the first is connected through hdmi and the second with rca. but it is working only if i adjust the video size to 480 or 576. is there something to solve this. i want to watch to my samsung d8000 using hdmi 1080p and for the other tv i don't care for the resolution.
thanks in advance!