unit = 0	tmu = 0		tmu0_source = 0		N/A
				tmu1_source = 1

    OpenGL[tmu0_source] active, Glide[0] active
	we have to send [tmu0_source] data to Glide[0]

		tmu = 1		tmu0_source = 1		switch
				tmu1_source = 0

    OpenGL[tmu1_source] active, Glide[1] active
	we have to send [tmu1_source] data to Glide[1]
	or we can send [tmu0_source:=tmu1_source] data to Glide[0] in passthrough mode


unit = 1	tmu = 1		tmu0_source = 0		switch
				tmu1_source = 1

    OpenGL[tmu1_source] active, Glide[1] active
	we have to send [tmu1_source] data to Glide[1]
	or we can send [tmu0_source:=tmu1_source] data to Glide[0] in passthrough mode

		tmu = 0		tmu0_source = 1		N/A
				tmu1_source = 0

    OpenGL[tmu0_source] active, Glide[0] active
	we have to send [tmu0_source] data to Glide[0]
