Sega Model 3¶
The peak of Sega arcade 3D (1996): PowerPC + Real3D graphics (Lockheed Martin, derived from military simulators), far ahead of its time. Virtua Fighter 3, Scud Race, Daytona USA 2, Sega Rally 2, Virtua Striker 2… In Steps (1.0 → 2.1).
Identification¶
| Field | Value |
|---|---|
| Manufacturer | Sega |
| Year | 1996 |
| Type | High-end 3D platform (multi-PCB) |
| Revisions | Step 1.0 / 1.5 / 2.0 / 2.1 |
| I/O | dedicated harness (Step 1.x) → JVS on some Step 2.x |
Architecture¶
| Block | Chip | Clock | Role |
|---|---|---|---|
| CPU | IBM PowerPC 603/603e | 66 MHz (Step 1.0) → 100 MHz (Step 2.x) | game logic |
| Graphics | Real3D Pro-1000 (Lockheed Martin) | textured polygons + Gouraud/specular, trilinear filtering, fog, lighting — derived from the military Real3D/100 | |
| Sound | Motorola 68000 + 2× SCSP (Yamaha) | + Digital Sound Board (DSB): 68000 + MPEG decoder for streamed music | |
| Tilegen / 2D | Sega customs | 2D planes + interface, protection |
The Real3D Pro-1000 comes straight from military flight simulators (General Electric/Lockheed): it handles textures, Gouraud shading, specular highlights, fog and trilinear filtering at a level unheard of in the arcade in 1996 (well beyond the consoles of the era).
Steps (revisions)¶
| Step | CPU | Sound / I/O | Games (examples) |
|---|---|---|---|
| 1.0 / 1.5 | PPC 66 MHz | SCSP (+DSB), dedicated I/O | Virtua Fighter 3, Scud Race / Sega Super GT, Le Mans 24 |
| 2.0 / 2.1 | PPC 100 MHz | richer 3D, JVS on some | Daytona USA 2, Sega Rally 2, Virtua Striker 2, Star Wars Trilogy, Spikeout |
Costly and rare boards, multi-PCB (CPU, Real3D video, sound); the Real3D customs are irreplaceable.
Notable games¶
Virtua Fighter 3 (1996), Scud Race / Sega Super GT, Le Mans 24, Daytona USA 2, Sega Rally 2, Virtua Striker 2, Lost World: Jurassic Park, Star Wars Trilogy Arcade, Spikeout, Dirt Devils, Harley-Davidson & L.A. Riders.
Security & preservation¶
- Protection: the Model 3 has security mechanisms (tilegen/crypt, encrypted data on some games) — hence emulation took a while.
- Emulation: the reference is Supermodel (a dedicated Model 3 emulator), which runs most of the catalogue; MAME support is partial. No FPGA/MiSTer core (PowerPC + Real3D far beyond the DE10-Nano).
- Maintenance: complex multi-PCB boards → methodical diagnosis; targeted recap, rare RAM/customs. 31 kHz monitor common (see CRT repair).
Common faults¶
| Symptom | Likely cause | Lead |
|---|---|---|
| No image / corrupt 3D | Real3D (Pro-1000), PowerPC, video RAM | Board-by-board diagnosis; Real3D customs irreplaceable |
| No streamed music | DSB board (68000 + MPEG) | DSB diagnosis |
| Partial sound | 2× SCSP | Sound-stage diagnosis |
| Freeze / reboot | RAM, multi-board power, heat | Reseat, RAM test, recap, ventilation |
| "Security" / tilegen | protection (encrypted data) | MAME/Supermodel document it; custom diagnosis |
Complex multi-PCB boards (CPU / Real3D / sound) → methodical diagnosis. A 31 kHz monitor is common. Real3D customs (military-derived) are near-unobtainable → preservation via Supermodel is advised.
EPROM repair¶
PowerPC 603 program. Mask ROM ROM board + boot EPROM; security via the game's ROM board. Scud Race, Virtua Fighter 3, Daytona USA 2, Sega Rally 2. No classic program EPROM — repair = the whole ROM board.
Modernisation & mods¶
The common ground for every JAMMA board
Video, power, control panel and upscalers depend on the cabinet rather than the board: everything is centralised in Modernising a cabinet. To run the board outside a cabinet (at home, on a display): supergun.
- Storage 🟡: the game lives in EPROM/mask ROM on the board. Changing or restoring a game means reprogramming the EPROMs (and, for a mask ROM, using a pinout adapter) → EPROM method.
- Media preservation: replacing the original storage, multicarts, ODEs and modern options by family → PCB preservation hub.
- Scan rate 📺: ~24.39 kHz / 57.5 Hz — medium resolution, ⚠️ a 15 kHz-only chassis will not do: you need a medium-res monitor or a tri-sync → tri-sync and upscalers.
(Computed from the MAME sources —
sega/model3.cpp— pixel clock ÷ htotal.) - FPGA / emulation: see the Emulation & FPGA section below.
Repair (technician)¶
- Costly multi-PCB (PowerPC 603 + Real3D video + sound): diagnose block by block; Real3D customs are rare and expensive (donor), careful inter-board connectors.
- ROMs sometimes encrypted per game → check the config before suspecting the logic.
- Sound: 68000 + 2× SCSP + DSB (MPEG) for streamed music.
- Capacitors: recap (old multi-PCB boards).
→ Methods: PCB fault-finding · Recap · EPROM · Traces & vias
Expected clocks — measurement table ✅¶
Values extracted from the MAME sources for this platform. On a scope or frequency counter, a clock that is missing or off-value points straight at the crystal, the divider or the chip at fault — the fastest starting point on a dead board.
| Component | Expected clock | Role |
|---|---|---|
| M68000 | 11.2896 MHz | main CPU |
How to read this table
Several values for one component = several board variants in this family (or several instances of the chip clocked differently). These frequencies are those of the clock signal at the component's input, not of its original crystal — on many boards the clock is divided down from a single master crystal.
Photos / assets¶
(To add: Model 3 set, PowerPC, Real3D board, DSB.)
Sources & attribution¶
- Wikipedia — Sega Model 3 (PowerPC 603, Real3D Pro-1000, Steps 1.0-2.1, SCSP+DSB, games) — CC-BY-SA — https://en.wikipedia.org/wiki/Sega_Model_3
- Supermodel — reference Model 3 emulator (hardware documentation)
- System16 — Sega Model 3 Hardware — to reference
- Internal page: Sega Model 2 (previous generation)
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.
Reading is open to everyone; posting requires signing in with Discord. Reports from the wiki's declared reviewers are handled first; anyone else's are read too, but go through a human before anything is changed.