Test Cases:

	RGB
		test 4 mux selection of parameters, do RGB at once
		check RGB clamped properly

	A
		test 4 mux selection of parameters

	2 cycle mode
		make sure texel0 (RGB & A) latched properly for 2 cycle
		vary 2nd cycle mode from 1st

	Chroma Keying
		both key and non key in 1 and 2 cycle mode
		check all paths of clamped minumum logic (9:3 reduction)
			check keying individually on all 3 components
			check key clamping (0, FF) on all 3 components

	Alpha Coverage
		alpha
		cvg*alpha
		cvg

	Texture Edge
		L >= 1
		L <= 1 w/alpha < 0.5 and alpha >= 0.5
		0 < L < 1, make sure result is clipped

Misc Info:

	if not in cov_time_alpha mode, combined alpha must != 0 since the
	circuit actually computes cvg*alpha/alpha and alpha just cancels out
	when it is non-zero.