Discrete logic and the 8080

The first arcade games of 1972 to 1978 come in two kinds. Pong and Breakout have no CPU. To reimplement them, you simulate the circuit. Space Invaders and the Midway 8080 boards run an Intel 8080 program beside analog sound circuits.

Board	Years	Main CPU and clock	Sound	Refresh	Protection	MAME status	Ghidra
Atari Pong, Breakout	1972 on	None (discrete logic)	Not covered here	Not covered here	None	Netlist emulation	Nothing to load
Midway 8080 black-and-white	1978 on	Intel 8080 at 1.9968 MHz	Analog circuits plus TI SN76477	about 59.54 Hz (computed)	None listed	In MAME	Built in (8085)

Atari Pong and Breakout

Hardware

Pong (Atari, 1972) has no CPU. MAME emulates it as a netlist of discrete logic. Breakout uses the same approach (MAME: atari/pong.cpp).

Protection

None listed.

Tools

MAME's netlist driver models the circuit. There is no program to decompile, so Ghidra and Unicorn do not apply.

Projects to learn from

MAME's pong.cpp netlist.

For an exact reimplementation

• Simulate the circuit. The game's behaviour comes from the logic gates, the counters and their timing.
• Use MAME's netlist as the description of the circuit.

Midway 8080 boards and Space Invaders

Hardware

Space Invaders (Taito, 1978; licensed to Midway in the US) uses an Intel 8080 CPU. Tomohiro Nishikado designed it. The game draws sprites with the help of a Fujitsu MB14241 shifter. Sound comes from analog circuits plus a TI SN76477 (Wikipedia (mirror): Space Invaders). Giant Bomb gives the Japanese release as 19 June 1978. Another source says November 1978 (Giant Bomb releases).

MAME's Midway 8080 black-and-white hardware uses a 19.968 MHz master clock. The CPU runs at master / 10, which is 1.9968 MHz. The pixel clock is master / 4. With totals of 320 by 262 the screen runs at about 59.54 Hz (computed) (MAME: midw8080/mw8080bw.h).

Protection

None listed.

Tools

• Ghidra decodes the 8080 with its built-in 8085 module.
• Unicorn has no 8080 backend. Take ground truth from MAME's debugger or from a small 8080 core (CPU families).
• The practices page has the full CPU table.

Projects to learn from

Computer Archeology hosts commented disassemblies of Space Invaders and Sea Wolf (Computer Archeology: Arcade).

For an exact reimplementation

• Run the port at about 59.54 Hz, the board's computed rate.
• Reproduce the MB14241 shifter as the game uses it.
• The sound is part circuit and part chip. An exact port needs a model of the analog sound as well as the 8080 code (Sound).