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Sega System 18 converts (de-suicide)

The System 18 is the successor to System 16B: same family, more layers (an extra Mega Drive-type VDP). Conversion-wise it's the same suicide story as System 16 — FD1094 — but with an extra trap: an Intel 8751 protection MCU. De-suicide is done with decrypted ROMs + removing the 8751 + bare 68000.

Field Value
Platform Sega System 18
Type FD1094 de-suicide + 8751 MCU removal
Difficulty 🟠
Suicide? Yes — FD1094 (battery-backed SRAM key) + 8751 MCU

Architecture (vs System 16B)

  • Enhanced System 16B base: main 68000 (often FD1094), Z80 sound, 2× YM3438 + Ricoh RF5C68 (PCM).
  • On top: a Mega Drive / Genesis-type VDP (315-5313) adding a graphics layer — hence the look of Moonwalker, Alien Storm, Shadow Dancer (richer sprites/planes than the 16B).

The dual protection

  1. FD1094: the program is encrypted, the key lives in the module's battery-backed SRAM. Dead battery = crash at boot (suicide). The encrypted code is in sockets A5 and A6 of the ROM board.
  2. Intel 8751: an MCU adding extra protection (memory control / anti-copy).

De-suiciding a System 18 (procedure)

To revive a suicided board (or run it battery-less):

  1. Replace the two encrypted EPROMs (A5 / A6) with their decrypted versions (MAME dumps).
  2. Remove the Intel 8751 MCU (the memory protection is no longer needed with decrypted code).
  3. Replace the FD1094 with a standard 68000 (no more decryption to do).

→ A board treated this way runs battery-less, permanently — but is no longer "original" (bare 68000 + decrypted EPROMs, 8751 absent). It's exactly the System 16 "ROM de-suicide", with the 8751 step added.

Spotting an already-de-suicided board

On an already treated board: the A5/A6 EPROMs are not Sega originals, the 8751 MCU is absent (empty socket), and the CPU is a standard 68000 instead of the FD1094. (Common on the second-hand market.)

The "original" alternative: FD1094 re-key

If you want to keep authenticity (encrypted FD1094), you can rewrite the key into the FD1094 module (Arduino method) instead of ROM de-suicide:

→ see System 16/18/24: FD1094/FD1089 (Arduino Mega 2560 re-key, hot battery swap). Note: on System 18 the 8751 then stays in place (original protection).

Converting to another game

Like System 16: either FD1094 re-key to the target game + that game's encrypted ROMs (original build), or bare 68000 + decrypted ROMs of the target game (+ handle the 8751 per game). Check the ROM board compatibility.

Program EPROM, game by game

System 18 ROM board: the program EPROMs sit on sockets A4-A7 (a single board family, unlike the 16B's four types). Size → EPROM: 128 KB → 27C010 · 256 KB → 27C020 · 512 KB → 27C040. Protection: FD1094 and/or 8751 depending on the game → de-suicide on this page, keys on the System 16 table. (Source: MAME sega/segas18.cpp.)

Game Program sockets (EPROM) Protection
Alien Storm A5/A6 = 27C020 FD1094 (set-dependent)
Bloxeed A5/A6 = 27C010 FD1094
Clutch Hitter A4/A5/A6/A7 = 27C020 FD1094
D.D. Crew A4/A5/A6/A7 = 27C020 FD1094
Desert Breaker A4/A5/A6/A7 = 27C040 FD1094
Laser Ghost A4/A5/A6/A7 = 27C020 FD1094
Michael Jackson's Moonwalker A5/A6 = 27C020 8751
Shadow Dancer A5/A6 = 27C020 FD1094
Where's Wally? (Wally wo Sagase!) A4/A6 = 27C020 FD1094

System 18 = possible double layer

Some games stack FD1094 (encrypted program) and 8751 (MCU). Full de-suicide = decrypted ROMs + bare 68000 and removing/handling the 8751 — see the procedure above.

Before / after

  • De-suicide: a dead board (FD1094 battery gone) lives again battery-less.
  • Re-key: the board stays a working encrypted original.

Where to read more

Sources & attribution

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

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