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Mattel Intellivision

The console that took on the Atari 2600 (1979). And technically it had the means: where everyone else was 8-bit, Mattel fitted a 16-bit processor — clocked, however, at under one megahertz.

Intellivision console with its two controllers

The Intellivision and its disc controllers. Photo by Evan-Amos (Vanamo Media), CC BY-SA 3.0.

Identification

Field Value
Manufacturer Mattel Electronics (USA)
Years 1979-1983
CPU General Instrument CP1610 @ ~895 kHz — 16-bit, colorburst ÷ 4
Video STIC (Standard Television Interface Chip) @ 3.579545 MHz
Sound AY-3-8914 @ ~1.79 MHz (colorburst ÷ 2)
Speech (option) SP0256 @ 3.12 MHz — Intellivoice module
Master crystal 3.579545 MHz — the NTSC colorburst
Media cartridge

A 16-bit machine in 1979 — but a slow one

General Instrument's CP1610 is a genuine 16-bit processor, released when the competition was 8-bit. The trade-off: it runs at about 895 kHz, the NTSC colorburst divided by 4.

In other words: do not expect a round megahertz. Measuring ~0.9 MHz on an Intellivision's CPU is the normal value.

Expected clocks — measurement table ✅

Component Expected clock Role
CP1610 ~894.9 kHz 16-bit CPU (3.579545 ÷ 4)
STIC 3.579545 MHz video
AY-3-8914 ~1.79 MHz sound (3.579545 ÷ 2)
SP0256 3.12 MHz speech — Intellivoice module only

Everything derives from the colorburst

The CPU, the STIC and the sound generator all come from the same 3.579545 MHz. A general clock failure therefore has one possible cause — while the speech module's SP0256 has its own crystal at 3.12 MHz.

The models

Model Year Notes
Intellivision 1979 the original
Intellivision (Sears) 1981 Sears-branded version
Keyboard Component 1981 ⚠️ see below
Intellivision II 1982 redesigned case
Intellivoice 1982 speech synthesis module
Entertainment Computer System (ECS) 1983 computer expansion

The Keyboard Component is a machine inside the machine

The Keyboard Component is not a mere keyboard: it carries its own processor — an M6502 — and a TMS9927 display controller, clocked from a separate 7.15909 MHz crystal.

In repair it is therefore a second complete system to diagnose on its own terms, with its own clocks.

The Intellivoice, and its quirk

The Intellivoice module adds an SP0256 — General Instrument's speech synthesiser.

An unusual operation, recorded by reverse-engineering

MAME's notes report that the module holds 64 ten-bit words which it simply serialises to the SP0256, and that the SP0256-012 blindly jumps to a fixed address when certain samples are played.

That is not a defect: it is how the chip is used. Odd speech behaviour therefore does not necessarily accuse the module.

Common faults

Symptom Probable cause Next step
Nothing starts 3.579545 MHz crystal CPU, STIC and sound derive from it together
CPU “too slow” nothing — ~895 kHz is the normal value See the box
No picture, sound fine STIC Custom chip with no replacement
No sound AY-3-8914 An AY-3-8910 variant, harder to source
No speech Intellivoice module or its 3.12 MHz crystal A crystal separate from the console's
Cartridge not read connector contacts Isopropyl alcohol, never an abrasive
Keyboard Component silent its M6502 or its 7.15909 MHz crystal A second system in its own right

Procedure — a dead console, step by step ✅

What this adds

Ordered for a console, not for an arcade board: what kills these is almost never the CPU. It is, in real order, the power supply, the capacitors, the drive or the cartridge slot, and only then the logic. → PCB diagnosis

1. The power supply. Two cases, depending on the machine. External brick: ⚠️ read the marking on the machine, next to the socket, and check the adapter against it — voltage and polarity. A centre-negative machine fed centre-positive loses its fuse, sometimes its regulator; do not trust a third-party label or a generic tip. Internal supply (the machine plugs straight into the wall): mains is inside the shell. Unplug, wait, and confirm the large capacitors are discharged before touching the board. Either way, measure under load: a failing supply holds its voltage until it is asked for current.

2. The fuse. Many of these machines have one right behind the socket — it is the part designed to die. Test it in continuity, out of circuit. A fuse that blows again is a short, not a fuse problem.

3. Capacitors. On most machines of this age this is the default suspect rather than a last resort — leaking SMD electrolytics eat the tracks underneath before they give any other sign. ⚠️ Not all of them are like that: some carry very few and are not recapped on principle. Read what this page says about it before reaching for the iron. → Recap

4. The cartridge connector. Cartridge contacts with isopropyl alcohol, never an abrasive eraser: it takes the gold plating off and the problem comes back worse. On the machine side, inspect the slot pins — splayed, bent or oxidised — and check continuity between slot and board.

5. Video output. Isolate the machine from the display: another cable, another TV, another input. A sizeable share of "dead consoles" are a dead cable, or a display that will not lock onto what this machine outputs — see the video section of this page for what that is.

6. Still nothing. Now, and only now, the logic: rails on the board, reset, clock, bus. → PCB diagnosis

Repair (technician)

  • One crystal for the console. A general failure has one cause — except on the modules, which have their own.
  • The CP1610 has no common replacement: it is an uncommon General Instrument processor, unlike the competition's 6502.
  • The AY-3-8914 is not an AY-3-8910: it is a variant, and substitution is not direct.
  • Diagnose the modules separately: Intellivoice and Keyboard Component each have their own clock.

→ Methods: PCB diagnosis · Recap

Modernisation & mods

  • No battery, no suicide.
  • Video output: RF as standard — composite/RGB mods exist in the community. → RGB & SCART
  • ⚠️ Do not host ROMs — method only.

Photos / assets

(To take: the main board with the CP1610 and the STIC, the Intellivoice module opened with its SP0256, and the Keyboard Component — a rare item — with its 6502.)

Archived technical documentation ✅

Manufacturer documentation archived locally: schematics, block diagrams, expected voltages, parts lists. The reference when a symptom matches no known fault.

  • Intellivision — PDF
  • Intellivision II — PDF
  • Intellivision ECS — PDF

Status

Manufacturer documents kept for preservation (machines out of production for decades), with no explicit licence — the same position as for the cabinet manuals already archived here.

Sources & attribution

Text (synthesised here; sources listed for attribution):

  • MAME — src/mame/mattel/intv.cpp (BSD-3-Clause / GPL): the CP1610 at 3.579545 MHz ÷ 4 annotated “Colorburst/4”, the STIC at the full colorburst, the AY8914 at colorburst ÷ 2, the SP0256 at 3,120,000 Hz for the Intellivoice; the Keyboard Component with its M6502 and TMS9927 at 7.15909 MHz ÷ 8; the model list (1979 original, Sears 1981, Keyboard Component 1981, Intellivision II 1982, Intellivoice 1982, ECS 1983); and the reverse-engineering notes on the speech module — 64 ten-bit words serialised to the SP0256, and the SP0256-012 jumping to a fixed address on certain samples — https://github.com/mamedev/mame/blob/master/src/mame/mattel/intv.cpp

Image:

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.