IGS011 (blitter hardware)¶
IGS's hardware before the PGM (1995-1997): Dragon World and its many revisions. A 68000, a custom blitter that doubles as protection, and a battery-backed main RAM — that last point deciding the board's fate.
Identification¶
| Field | Value |
|---|---|
| Manufacturer | IGS (Taiwan / China) |
| Years | 1995-1997 |
| CPU | M68000 @ ~7.33 MHz (22 MHz crystal ÷ 3) |
| Blitter | IGS011 @ 22 MHz — blitter and protection |
| Protection | IGS003 (8255 + protection) · IGS012 (protection, optional) |
| Sound | OKI M6295 @ ~1.05 MHz (22 ÷ 21) + YM3812 — or ICS2115, board depending |
| Save | ⚠️ battery on the main RAM |
| PCB format | JAMMA |
A division by 3, then by 21
The ratios are unusual: the 68000 runs at 22 MHz ÷ 3 and the OKI at 22 MHz ÷ 21. These are not round divisions — measuring 7.33 and 1.05 MHz is normal.
Expected clocks — measurement table ✅¶
| Component | Expected clock | Role |
|---|---|---|
| M68000 | ~7.33 MHz | Main CPU |
| IGS011 | 22 MHz | blitter and protection |
| OKI M6295 | ~1.05 MHz | ADPCM |
⚠️ A battery on the main RAM¶
This is the thing to know before buying or storing one of these boards.
It is not a settings battery
On this hardware the battery backs the main RAM — not a simple bookkeeping EEPROM. A dead battery therefore does not clear high scores: it empties a memory the board depends on to work.
On top of that, the IGS011 blitter itself performs a protection function, and the games' code is encrypted — it had to be decrypted for them to be preserved.
The useful move is the same as everywhere: take the battery out before it leaks, and do not let a board of this family sit for years unchecked. → Backup batteries
Three customs, three roles¶
| Custom | Role |
|---|---|
| IGS011 | blitter and protection |
| IGS003 | 8255 (I/O) and protection |
| IGS012 | extra protection — fitted only on some boards |
→ The combination varies between revisions of the same game. The MAME driver records, revision by revision, which chips are fitted and on which board part number.
Notable games¶
Dragon World and its many regional revisions (V010C, V011H, V020J, V021O, V030O, V040O…), on the NO-0105-x and NO-T0105 boards.
Revisions are not interchangeable
Each Dragon World version has its own combination of customs and its own board part number. A part taken from one revision will not necessarily suit another.
Common faults¶
| Symptom | Probable cause | Next step |
|---|---|---|
| Corrosion near the battery | battery on the main RAM | Take the battery out before any diagnosis |
| Will not boot after storage | main RAM emptied | See the box |
| Corrupt graphics | IGS011 blitter | No replacement: comparison is mandatory |
| Protection check failed | IGS003 or IGS012 | Check which chips are fitted on your revision |
| No sound | OKI M6295, YM3812 or ICS2115 | The sound stage varies by board |
Repair (technician)¶
- The battery first. It is the part that decides whether the board survives.
- Identify the revision before comparing: the board part number and the custom line-up change from version to version.
- No IGS custom has a replacement — the same situation as on the PGM and the PGM2.
→ Methods: PCB diagnosis · Recap · Backup batteries
Procedure — a dead board, step by step ✅¶
What this adds
The general method lives in PCB diagnosis. This is its application to this platform: the same order, but with the values actually expected here, so you do not have to go back and forth.
Tools: multimeter, oscilloscope (or frequency counter), current-limited bench supply, desoldering braid. → Tooling
If the board is still in a cabinet
A CRT holds its charge with the machine unplugged. → CRT safety
1. Inspection, power off. Corrosion, cut tracks, oxidised EPROM legs, leaking SMD capacitors, dubious earlier repairs.
2. The connector, before anything else. A large share of "dead boards" are a contact problem, not a fault. Clean the contacts with isopropyl alcohol and reseat — not with an abrasive eraser on a gold edge, which takes the plating off and brings the problem back worse. It costs two minutes and settles the question.
3. Power, measured on the board. Aim for +5.0 V measured as close as possible to where power reaches the board — not at the PSU output: the drop is in the loom, and that is exactly what makes a board boot on the bench and not in the cabinet. Where you probe depends on this board's connector — JAMMA edge, JVS loom or a proprietary harness — plenty of makers kept one long after JAMMA arrived — see Identification above. → Wiring Check −5 V and +12 V too if the sound stage uses them. Suspected short: bring it up current-limited and find the hot spot.
4. /RESET. It must release after power-up. Held low = the CPU never starts. A 1–2 Hz loop is not the reset circuit, it is the watchdog: the CPU is crashing at boot, so look at the bus, not at the reset.
5. Clocks — the values expected on this platform.
- M68000 → ~7,33 MHz (Main CPU)
- IGS011 → 22 MHz (blitter et protection)
- OKI M6295 → ~1,05 MHz (ADPCM)
No clock on the M68000 (~7,33 MHz) and there is no point measuring anything else: the fault is the crystal, the divider, or the chip itself. That single measurement splits a dead board in two.
6. Bus. Activity on the main CPU's address lines tells you whether it is running or frozen. Frozen with good clocks and good reset → work RAM, bus buffers, ROMs.
7. It boots but the picture or the sound is wrong — that is another job: see Common faults on this page, then signal tracing.
Modernisation & mods¶
- Indirect suicide 🟠: the battery holds no key, but it holds the main RAM.
- ⚠️ Do not host ROMs — method only.
Emulation & FPGA¶
MAME covers the platform (igs/igs011.cpp, driver by Luca Elia, code decrypted by
Olivier Galibert). That decryption work is what made these games preservable.
Photos / assets¶
(To take: the IGS011 blitter, the battery and its surroundings, and the silkscreened NO-0105-x board part numbers.)
Sources & attribution¶
Text (synthesised here; sources listed for attribution):
- MAME —
src/mame/igs/igs011.cpp(BSD-3-Clause / GPL, driver by Luca Elia, code decrypted by Olivier Galibert): 68000 at 22 MHz ÷ 3, IGS011 at 22 MHz, OKI M6295 at 22 ÷ 21; the three customs' roles — IGS011 (blitter and protection), IGS003 (8255 and protection), IGS012 (optional protection); “NVRAM: Battery for main RAM”; and the revision-by-revision survey tying each Dragon World version to its board part number (NO-0105-x, NO-T0105), its sound stage and its protection chips — https://github.com/mamedev/mame/blob/master/src/mame/igs/igs011.cpp
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.