Namco Custom Chips

Galaga, and most Namco licensed boards of the era, use a number of Custom ICs to provide functionality (and I guess to try and confuse the bootleggers of the day 🙂 )

These ICs often just need cleaning, but as they are very fragile it’s good to know what they do when diagnosing a board.

Here’s a table from of each numbering, and it’s purpose

Number Short Name Description
54xx   Sounds Generates Explosion Sounds (possibly a custom Z-80?) [Mux 4 Channel Audio Generator]
53xx   Steering Input [Custom 4Bit Micro/Handles Steering/sw/read]
52xx   Audio Processor [Audio Processor 4 Bit Voice]
51xx   Input Player controls, DIP switches, etc [Custom 4 bit I/O – Coins]
50xx   Sound Sequencer [Sound Sequencer]
13xx   Horizontal Scroll [Horizontal Scroll]
12xx   Sprite Position [M.OBJ. Position]
11xx   Playfield Shift Register [Datashift Playfield Register]
10xx   Micro Buffer Data [Micro Buffer Data]
09xx   Sprite Ram Buffers [M.OBJ Ram Buffers]
08xx   Bus Controller (basically the same as Pacman’s “285” Sync Buss Controller) [Multi-CPU Bus Controller]
07xx   Clock Divider (generates horizontal and vertical timing pulses divided down from master clock) [Sync Generator]
06xx   Bus Interface [Custom 50’s Controller]
05xx   Star Generator (tapped pseudo-random feedback shifter– makes scrolling starfield)
04xx   Bus Interface Motion object and scratch RAM to CPU bus interface [M.Obj Controller]
03xx   Buffer, Playfield Data [Buffer, Playfield Data]
02xx   Custom Shifter Custom shift register for data from graphics ROMs [Shift Register]
00xx   VRAM Addresser (basically the same as Pacman’s “284” VRAM Addresser) [Video Ram Addresser]

There is also a very interesting document archived on the web of what each of these chips actually does on each pin, and I guess then how to recreate them.

I’m attached it here – Namco [Custom Chips] [English] – so that I have it available going forwards

and here’s an example of the replacement chips that Jrok and others are making – very cool

Jrok Custom 51

and the standard Galaga custom chips versus replacements


Standard Galaga CPU Board

Standard Galaga CPU Board


Jrok GAL Replacements

Jrok GAL Replacements


Namco Custom Chips

Reverse engineering a Namco custom chip

Replacement Namco custom chips by Jrok

Mike’s arcade sells the above Jrok chips

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