What Is an Arcade Daughterboard and How Does It Work on an Original PCB?

By HighScoreSaves Technical Team

Reviewed and updated August 19, 2026

An arcade daughterboard is a secondary circuit board that plugs into a specific location on an original arcade PCB to add or extend functionality without replacing the game board itself.

Many HighScoreSaves kits use a daughterboard at the original CPU location. The original processor is carefully removed from the arcade PCB, installed on the daughterboard, and the daughterboard is then installed into the original CPU socket. The original arcade PCB remains the primary game hardware.

This guide explains what a daughterboard is, how it interfaces with original arcade hardware, why Pin 1 orientation and socket condition matter, and what to verify before applying power.

Arcade Daughterboards at a Glance

A daughterboard is an additional circuit board that connects to the original arcade PCB.
Many HighScoreSaves daughterboards install at the original CPU socket.
The original CPU is normally installed on the daughterboard unless the product page states otherwise.
The original arcade PCB continues to provide the game hardware and electrical environment.
Pin 1 must align correctly between the original PCB, daughterboard, and CPU.
Every daughterboard pin must enter the correct socket opening.
A damaged or unreliable CPU socket can prevent a properly installed daughterboard from working correctly.
Some kits also use adapters, ribbon cables, or game-specific connections.
The product page and game-specific installation guide are the final authority for each kit.

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What a Daughterboard Is Why Daughterboards Are Used Original PCB Role CPU Installation Path Pin 1 Orientation Socket Condition Proper Seating Adapters Reversibility Troubleshooting Final Checklist Support

What Is an Arcade Daughterboard?

A daughterboard is a smaller circuit board designed to connect to another circuit board. In classic arcade hardware, it can add circuitry, memory, control logic, storage, game-selection functions, or other features while leaving the original game PCB in place.

The term describes the physical relationship between the boards: the daughterboard depends on the original PCB and connects through a socket, header, adapter, ribbon cable, or another defined interface.

It is not a replacement arcade PCB. The original board still supplies the hardware environment that the kit was designed to use.

Why Daughterboards Are Used in Arcade Upgrade Kits

A daughterboard allows additional circuitry to be added without permanently replacing the original game board. Depending on the kit, that circuitry may provide features such as high score saving, Free Play, additional game versions, menu settings, ROM Saver functions, or other game-specific upgrades.

This approach keeps the upgrade tied to the original arcade hardware rather than substituting a modern emulation platform for the original PCB.

The exact functions vary by game and kit, so the specific product page should always be checked for supported features.

The Original Arcade PCB Still Does the Work

Installing a daughterboard does not turn the cabinet into a different hardware platform. The original arcade PCB remains installed and continues to provide the game-specific circuitry, timing, audio, video, inputs, outputs, memory, custom logic, and other hardware used by that game.

The daughterboard interfaces with that original hardware at a defined connection point. On many HighScoreSaves kits, that point is the original CPU socket.

This is why compatibility depends on the exact original PCB, processor, socket arrangement, and board revision rather than only on the cabinet title or artwork.

How the CPU Moves from the Original PCB to the Daughterboard

On many HighScoreSaves installations, the original socketed CPU is carefully removed from the arcade PCB. The processor is then installed into the CPU socket on the daughterboard.

The daughterboard has pins or a header that plug into the original CPU socket on the arcade PCB. Electrically, the daughterboard is now positioned between the original processor and the original board while maintaining the required connections.

Some kits use a different arrangement, so never assume the CPU must be moved unless the product page and installation guide specifically instruct you to do so.

Pin 1 Must Be Correct at Both Levels

A daughterboard installation usually requires two separate orientation checks. First, Pin 1 on the daughterboard must align with Pin 1 on the original PCB socket. Second, Pin 1 on the original CPU must align with Pin 1 on the daughterboard CPU socket.

A daughterboard can be installed correctly while the CPU on top of it is backward. The reverse is also possible: the CPU can be correctly oriented on the daughterboard while the daughterboard itself is backward in the original PCB.

Verify every notch, molded dot, printed Pin 1 marking, socket orientation, and installation-guide photo before applying power.

The Original CPU Socket Must Be Reliable

The daughterboard depends on the original CPU socket for both electrical contact and mechanical support. A cracked socket, weak contact, corrosion, damaged solder joint, lifted pad, or previous repair can cause a properly installed kit to behave incorrectly.

Inspect the socket before installation and check the solder side of the PCB when its condition is uncertain. Do not force a daughterboard into a damaged or unusually tight socket.

If the socket cannot provide a dependable connection, repair the original PCB before installing the upgrade kit.

Proper Daughterboard Seating

Before pressing the daughterboard into the socket, check both rows of pins from above and from the side. Every pin must line up with the correct socket opening.

Apply even pressure so the board seats squarely. One end should not be fully inserted while the opposite end remains raised. Check for pins that are bent outward, folded underneath, or sitting beside the socket instead of inside it.

A daughterboard that is crooked, unusually loose, or difficult to seat should be removed and inspected before power is restored.

Some Kits Use Adapters or Additional Connections

Not every arcade PCB presents the same CPU layout or electrical interface. Some upgrade kits therefore use a game-specific adapter between the original PCB and the daughterboard.

Other kits may include ribbon cables, headers, additional plugs, ROM-related connections, or other components required by that game. Each connection has its own orientation and installation requirements.

Follow the exact order shown in the game-specific installation guide rather than assuming that one kit installs the same way as another.

Daughterboard Upgrades and Original Hardware Preservation

A socket-based daughterboard installation can often be removed later so the original CPU can be returned to its original socket. This allows the original arcade PCB to remain the foundation of the game instead of being replaced by a different board.

However, reversibility depends on the condition and configuration of the specific PCB. Some boards may require socket repair, an adapter, or another game-specific step before installation.

Avoid unnecessary modifications that are not called for by the installation guide.

If the Game Does Not Boot After Installation

Disconnect power before making any changes. Recheck the daughterboard orientation, CPU orientation, every header pin, the original CPU socket, adapter connections, and any game-specific ROM or cable steps required by the installation guide.

Look closely for one pin outside the socket, a pin folded under the daughterboard, a CPU pin that missed its socket opening, or a board that is not fully seated.

When compatibility or installation remains uncertain, send clear photos of the complete PCB, CPU area, daughterboard, socket, Pin 1 markings, and all connections to HighScoreSaves before repeatedly applying power.

Final Daughterboard Checklist Before Power-Up

The cabinet is unplugged during installation.
The exact original PCB and supported kit have been confirmed.
The original CPU socket is clean and mechanically sound.
Pin 1 on the original PCB socket has been identified.
Pin 1 on the daughterboard has been identified.
Pin 1 on the original CPU has been identified.
The daughterboard is oriented correctly in the original PCB socket.
The CPU is oriented correctly in the daughterboard socket.
Every pin is inside the correct socket opening.
The daughterboard is fully and evenly seated.
All adapters, ribbon cables, ROM changes, or additional connections match the installation guide.
No uncertainty remains before power is restored.

Product Pages and Installation Guides Are the Final Authority

Daughterboard design, CPU location, adapter requirements, ROM changes, supported PCB revisions, and installation steps vary from game to game.

Always use the specific HighScoreSaves product page and game-specific installation guide for the exact kit being installed. Those instructions are the final authority for compatibility and installation.

Technical Support

If the daughterboard orientation, CPU socket condition, processor type, adapter arrangement, or PCB compatibility is uncertain, stop before applying power.

Email is the preferred support method. Contact sales@highscoresaves.com and include clear photos of the complete PCB, CPU area, original CPU socket, daughterboard, Pin 1 markings, adapters, and all related connections.

Disconnect cabinet power before removing a CPU or installing a daughterboard. Verify the exact PCB, socket condition, Pin 1 orientation, daughterboard seating, CPU orientation, and all game-specific connections before applying power.