The very beginning of Sega arcade (via Gremlin, 1977-1979): a simple Z80
platform, often black & white with colour overlays, behind classics like
Carnival, Head On and Frogs. Historically important — and a MiSTer core
exists.
The VIC Dual board (Sega / Gremlin, 1977-79). Photo uploaded by Black Squirrel to Sega Retro, a site under CC BY 4.0.
The name comes from the "VIC" video chip; "Dual" because it was designed for two
players. One of Gremlin/Sega's first standardised platforms — emulated in MAME
(sega/vicdual.cpp).
Head On (1979, an ancestor of Pac-Man's "collect along a route" idea), Carnival
(1980, a shooting gallery), Frogs (a Frogger ancestor), Depthcharge, Safari,
Invinco, N-Sub, Borderline, Digger…
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 📺: ~15.72 kHz / 60.0 Hz — standard resolution, a classic 15 kHz chassis is fine → tri-sync and upscalers.
(Computed from the MAME sources — sega/vicdual.cpp — pixel clock ÷ htotal.)
FPGA / emulation: see the Emulation & FPGA section below.
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
Z80
1.93356 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.
31 games on this platform, settings extracted from the MAME sources (INPUT_PORTS_START blocks). The Position column gives the switch's physical reference on the board (SW2:!3,!4 = bank SW2, levers 3 and 4) — which is what lets you set it up without the paper manual. Games are sorted by MAME set name.
These settings apply to the game and revision described by MAME. One title may have several DIP sets depending on region or revision, and some systems use soft-dips (settings in memory, via the test menu) rather than physical switches. In case of a discrepancy, the board's silkscreen and the test menu are authoritative.
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.
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.
Z80 → 1.93356 MHz(Sound CPU (usually))
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.
1977-80 boards: 8080/Z80 program in tiny 2708 / 2716 EPROMs (1-2 KB), many of them (e.g. Carnival ≈ 16× 1 KB). Colour PROMs. Mind the period components (multiple ±5/±12 rails).
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.
