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Konami GX / Viper converts

Two Konami generations built around a common motherboard + swappable game carrier: the System GX (1994, ROM board) and the Viper (1999, CF card). On both, "changing game" comes down to the right carrier plus a reset (EEPROM / RTC).

Konami System GX

Field Value
CPU 68EC020 @ 24 MHz
Sound CPU 68000 @ 16 MHz
Media ROM board (sub PCB) plugged into the motherboard
Difficulty 🟡🟠 (ROM board swap + EEPROM reset ; orientation!)

Motherboards & ROM boards

  • Motherboard: Type 1 (PWB354192C, larger, runs hot) or Type 2 (PWB300456A, more compact).
  • Sub PCB (the game's ROM board): Type 1 (K053936 "rozz"/rotation chip, analog inputs, LAN option), Type 2 (PWB454204A/B, stock, sometimes protection chips on the ROM board), Type 3 (dual monitor, K053936, external palette RAM), Type 4 (PWB301798A, dual monitor, DMA protection).

Swapping / converting a GX

  1. Pick a compatible ROM board: Type 2 boards are fully interchangeable between motherboards.
  2. Reset the EEPROM: hold the TEST switch down at power-on when changing game.
  3. Check for possible protection on the ROM board (some Type 2).

Mounting orientation (Type 1/3/4)

On a Type 1 motherboard, the Type 1/3/4 sub PCBs have a forced mounting direction: they plug in both ways, but do not work — and can be damaged — if fitted the wrong way (on top). Check the key/direction before powering on.

GX program EPROM, game by game

The 68EC020 program lives on the ROM board (types 1-4, see above). EPROM: 128 KB → 27C010 · 512 KB → 27C040 · 1 MB → 27C080 · 2 MB → 27C160 (16-bit). Most "Type 1" GX = 2× 27C040. (Source: MAME konami/konamigx.cpp. Board view: Konami GX PCB.)

Game Program EPROM
Gokujō Parodius / Fantastic Journey 2× 27C040
Sexy Parodius 2× 27C040
Salamander 2 2× 27C040
Twin Bee Yahhoo! 2× 27C040
Daisu-Kiss 2× 27C040
Crazy Cross / Puzzle De Pon 2× 27C040
Taisen Tokkae-dama 2× 27C040
Winning Spike 2× 27C040
Dragoon Might 2× 27C040 + 2× 27C080
Run and Gun 2 / Slam Dunk 2 2× 27C040 + 2× 27C080
VS Net Soccer 2× 27C040 + 2× 27C080
Racin' Force 2× 27C040 + 2× 27C160
Soccer Superstars 4× 27C040
Golfing Greats 2 (Open Golf) 6× 27C040
Lethal Enforcers II 4× 27C010

GX = ROM board type + EEPROM reinit

Converting a GX: you need the right ROM board type (1-4) for the target game, and to reinitialise the EEPROM (hold TEST at power-on) — mind the orientation (Type 1/3/4). See the GX section above.

Konami Viper (1999)

Field Value
Base PowerPC (Konami 3D system)
Media CF card (via a PCMCIA → CF adapter)
Security DS2430 EEPROM on the motherboard + RTC
Difficulty 🟡 (CF swap + RTC + EEPROM reset)
  • The game software lives entirely on the CF card (32M / 64M / 128M), in one PCMCIA slot fitted with a CF adapter.
  • Security: a DS2430 (1-wire EEPROM) on the motherboard. Most games accept any DS2430; only Police 911 2 uses a dedicated dongle.

Swapping a Viper game

You can swap CF cards provided you:

  1. Change the CF card (target game image),
  2. Change the matching RTC (clock),
  3. Reset the motherboard EEPROM.

→ The CF + RTC + EEPROM reset combo = the Viper "game swap methodology".

Before / after

  • GX: the motherboard runs a different game via a compatible ROM board (Type 2 ideally) + EEPROM reset.
  • Viper: a Viper cabinet changes game by CF card (+ RTC + EEPROM).

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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