Graphic EPROMs: 2x TMS2716

Code EPROMS: a row (labeled as X) added to the Z80 side of the PCB. This
row is populated with 10 x 2708 EPROMs, 2 x 74LS365 additional address buffers,
1 x 74LS138 decoding the 0h to 1FFFh range and 1 x 74LS139 decoding the
2000h to 27FFh range (2 more 2708 places are empty, so this LS139 can decode
up to 2FFFh.

Label	Pos	Addr
20	X1	   0h
21	X2	 400h
22	X3	 800h
23	X4	 C00h
24	X5	1000h
25	X6	1400h
26	X7	1800h
27	X8	1C00h
28	X9	2000h
29	X10	2400h