Colorful blocks and stripes upon boot. Will not start.

My suspicion is the logic board, but if there's anything else it could be i'd rather test that first. Upon startup there is nothing but bluish blocks with white stripes, and then to the side multi-colored stripes. If I hold the power button down for 10 seconds I get a loud noise and a flashing light (where it glows when you put it to sleep). Beyond that it just stays that way, except occasionally when it's left long enough for the screen to dim it fades to a grayish white with flickering colors and pixels running through the center. It had started overheating, and the fans ran constantly regardless of temperature for about 4 weeks before this happened, but other than that behaved fine. Exactly what is it? Is it the logic board?