# this document is not going to be of much use to you unless you have
# the schematics and follow along.
# Gyruss ROM files from TANT archive
GYA-1.BIN - 11J - CPU Z80, 8K, Addr 0000 - 1FFF
GYA-2.BIN - 12J - CPU Z80, 8K, Addr 2000 - 3FFF
GYA-3.BIN - 13J - CPU Z80, 8K, Addr 4000 - 5FFF
GY-5.BIN - 18E - CPU 6809, 8K, Addr 0000 - 1FFF
GY-6.BIN - 02H - Graphics ROM
GY-7.BIN - 5B/6C - Graphics ROM, 8K Bank 1, MSB
GY-8.BIN - 6B/7C - Graphics ROM, 8K Bank 0, MSB
GY-9.BIN - 7B/8C - Graphics ROM, 8K Bank 1, LSB
GY-10.BIN - 8B/9C - Graphics ROM, 8K Bank 0, LSB
GY-11.BIN - 6A - Audio Z80, 8K, Addr 0000-1FFF
GY-12.BIN - 8A - Audio Z80, 8K, Addr 2000-3FFF
GY-13.BIN - 11H - Audio 8039, 4K, Addr 0000 - 0FFF
# Gyruss CPU board memory map, gleaned from the schematics ...
#
#Addr Chip Loc Romfile? Description
#-------- ---- ---- ---------- -----------
0000-1FFF 2164 11J GYA-1.BIN 8k EPROM
2000-3FFF 2164 12J GYA-2.BIN 8k EPROM
4000-5FFF 2164 13J GYA-3.BIN 8k EPROM
6000-7FFF 2164 14J N/C 8k EPROM
8000-87FF 2128 17C 2KB RAM, shared w/6809
8800-8FFF aliased ram
9000-9800 2128 5J,3J,2J 6KB SRAM
A000
B000
C000
D000
E000
F000
#
# CPU Board custom "6809"
#
0000 \_ /VCOUNT = 0, R/O places contents of 819:825 on data bus
1000 /
2000 \_ /9IRQ = 0
3000 /
4000 \_ SRAM @ 14A,13A,12A,11A MUXED with sprite generator. Even / Odd
5000 / Data is split between X and Y; X related to cols, Y related to rows
6000 \_ /9ZRAM -- Accesses 2K shared memory between Z80 and 6809
7000 /
8000 \
9000 |
A000 \ _ Not mapped.
B000 /
C000 |
D000 /
E000 \_ Program ROM, 8k 2764 (E000 - FFFF)
F000 /
Not having the board in front of me, I would probably be inclined to start by checking the SRAMS at 11-14A first, replace them if you can, and work backwards through the TTLs between them and the CPU if replacement does not fix.
Not much going on on this board, a few minutes with a logic probe may find a stuck input or output / shot TTL on the board. I'm finding this increasingly common these days. Good news is that it boots and doesn't watchdog. This takes a lot of stuff off the suspect list. And likely means it's not the shared SRAM or main program RAM.