Sega Model 2¶
Sega's 3D monster (1993), with the GE Aerospace / Martin Marietta heritage: the first arcade hardware to do real-time texture-mapping + filtering. Daytona USA, Virtua Fighter 2, Sega Rally, Virtua Cop, House of the Dead… A massive success (130,000+ boards), in four variants.
Identification¶
| Field | Value |
|---|---|
| Manufacturer | Sega |
| Year | 1993-94 |
| Type | Texture-mapped 3D platform (+ bilinear filtering) |
| Variants | Model 2, 2A-CRX, 2B-CRX, 2C-CRX |
| I/O | dedicated Sega I/O board (digital/analog) — predates JVS |
Architecture¶
| Block | Chip | Clock | Role |
|---|---|---|---|
| CPU | Intel i960KB (RISC) | ~25 MHz | game logic |
| 3D geometry | Fujitsu TGP (MB86234/86235) | polygon transforms/projection | |
| Graphics | textured engine (Compu-Scene, GE/Martin Marietta tech) | texture-mapping + filtering/anti-aliasing — a major leap over the Model 1 (untextured) | |
| Sound | Motorola 68000 + Sega MultiPCM (315-5560) → SCSP (2B/2C) | + optional Digital Sound Board (DSB): 68000 + MPEG decoder for streamed music (Daytona, Sega Rally) |
The Model 2's decisive contribution is texture filtering (bilinear): textures no longer "shimmer" like on rivals, hence the "smooth" look characteristic of Daytona USA / Virtua Fighter 2.
Variants (the real topic)¶
| Variant | Year | Geometry stage | Sound | Examples |
|---|---|---|---|---|
| Model 2 (original) | 1993 | i960 + 2× TGP | MultiPCM | Daytona USA, Virtua Cop, Desert Tank |
| 2A-CRX | 1994 | i960 + TGP, revised layout | MultiPCM (+ DSB) | Virtua Fighter 2, Sega Rally, Virtua Cop 2, Manx TT |
| 2B-CRX | 1995 | SHARP geometry coprocessor (replaces the TGPs) | SCSP (Saturn-style) | Fighting Vipers, Virtual On, Sonic the Fighters, Dead or Alive, The House of the Dead, Last Bronx |
| 2C-CRX | 1996 | single geometry custom | SCSP | Overrev, Top Skater, Sky Target |
The variants mainly change the geometry stage (TGP → SHARP → custom) and the sound (MultiPCM → SCSP). Textured rendering stays the trademark.
Notable games¶
Daytona USA (1994), Virtua Fighter 2 (1994), Sega Rally Championship (1994), Virtua Cop 1/2, Fighting Vipers, Virtual On: Cyber Troopers, Sonic the Fighters, Dead or Alive (1996), The House of the Dead (1997), Last Bronx.
Security & preservation¶
- Protection: several Model 2 games carry a custom security chip (the program talks to it) — reverse-engineered by the community for emulation.
- Emulation: the Model 2 is well emulated — by MAME and above all by the MODEL2 Emulator (ElSemi), the historic reference for this platform. No FPGA/MiSTer core (i960
- TGP too complex).
- Customs hard to source (i960, TGP, graphics customs) → mind the contacts, the power, targeted recap depending on age. Dedicated 24/31 kHz monitor.
Common faults¶
| Symptom | Likely cause | Lead |
|---|---|---|
| No image / corrupt 3D | i960, TGP/SHARP, video ASIC | Board-by-board diagnosis (CPU / video); rare customs |
| No streamed music | dead DSB board (68000 + MPEG) | DSB diagnosis (MPEG-music games: Daytona, Sega Rally) |
| Partial sound | MultiPCM (2/2A) or SCSP (2B/2C) | Sound-stage diagnosis per variant |
| Crash / freeze | RAM, power, multi-board interconnects | Reseat, RAM test, targeted recap |
| "Security check" | the game's custom security chip | Check the chip; MAME documents the exchange |
A multi-board set → methodical board-by-board diagnosis. A dedicated 24/31 kHz monitor.
EPROM repair¶
i960 program. ROM board with boot EPROM + mask ROM (data/3D). Virtua Fighter 2, Daytona USA, Sega Rally, Virtua Cop. Repair = the game's ROM board; security via the board (no isolated classic program EPROM).
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/model2.cpp— pixel clock ÷ htotal.) - FPGA / emulation: see the Emulation & FPGA section below.
Repair (technician)¶
- Multi-PCB (i960 CPU + TGP/SHARP geometry + video ASIC + sound): diagnose board by board; geometry customs are rare (donor).
- Digital Sound Board (DSB): missing streamed MPEG music = DSB 68000 + MPEG decoder (daughterboard), independent of the SCSP.
- Sound: 68000 + MultiPCM → SCSP (2B/2C) — diagnose the sound stage.
- Capacitors: recap; dedicated Sega I/O (pre-JVS): check contacts/connectors.
→ 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 |
| Z80 | 4 MHz | sound CPU (usually) |
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.
Original manuals for games on this platform ✅¶
Manufacturer manuals for games running on this board. Beyond the instructions, they very often carry the full DIP settings, the connector pinout, the test procedure, the parts list and the expected voltages.
- Daytona USA — original manual (PDF)
→ Full catalogue: service manuals, wiring & game manuals
Photos / assets¶
(To add: Model 2 / 2A / 2B board, i960, TGP, DSB.)
Sources & attribution¶
- Wikipedia — Sega Model 2 (i960 + TGP, texture-mapping + filtering, 2/2A/2B/2C variants, MultiPCM/SCSP/DSB, games) — CC-BY-SA — https://en.wikipedia.org/wiki/Sega_Model_2
- MODEL2 Emulator (ElSemi) — reference emulation of the platform
- System16 — Sega Model 2 Hardware — to reference
- Internal page: Sega Model 1 (previous, untextured 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.