0x41 - ??? not currently used
0x44 - sda pointer for S-DD1 graphics
0x47 - preset
0x50 - ??? (Joe & Mac = 1E)
0x53 - ??? not currently used
0x55 - ??? maybe sfx clock speed
0x61 - ??? not currently used
0x63 - 01 = hirom, if missing or 00, lorom
0x65 - special chip
0x68 - ??? overscan? (0, 1, 2...