Fujitsu FM-7 / FM-8 (& FM77)¶
Fujitsu's 6809 line (FM-8 in 1981, FM-7 in 1982) — a dual-6809 architecture (main CPU + video sub-CPU), popular in Japan for 8-bit games before the FM Towns. Standard JP 8-bit repair: recap, drive, keyboard.
Fujitsu FM-New7 (série FM-7) — photo by JCCyC, CC BY-SA 3.0 (Wikimedia Commons).
Identification¶
| Model | Year | Note |
|---|---|---|
| FM-8 | 1981 | dual 6809, optional bubble memory |
| FM-7 | 1982 | consumer version, the gaming reference |
| FM77 / FM77AV | 1984-85 | built-in floppy, AV = 4096 colors, FM sound |
CPU: two Motorola 6809 (main + video); Sound: PSG (AY-3-8910) then FM (YM2203) on AV; RGB output; cassette / floppy.
Clocks & frequencies ✅¶
| Component | Frequency | Role / scope |
|---|---|---|
| Motorola MC68B09 | 2 MHz | CPU principal |
| Motorola MC68B09 | 2 MHz | second 6809 dédié au graphisme |
| Zilog Z80 | — | en option, sur carte d'extension enfichable |
The FM-7 is a twin 6809 at 2 MHz machine: a main processor and a separate graphics processor. A purely video symptom can therefore come from the second 6809 while the main one is fine.
Why this matters in repair
A clock that is missing or off-value on a frequency counter points straight at the crystal, its divider chain or the component it feeds — the fastest starting point on a machine that will not boot. Source: Wikipedia (CC-BY-SA).
Repair (technician)¶
- Recap (PSU + board) → Recap.
- Floppy drive (FM77): mechanism / belts → clean, Gotek possible.
- Dual 6809: on a crash, isolate main vs sub-CPU → substitution.
- Keyboard: contacts → clean.
- Video: RGB output / palette (AV) → check wiring.
Common faults¶
| Symptom | Likely cause | Lead |
|---|---|---|
| Won't boot / freezes | one of the two 6809 / RAM | Isolate, substitute |
| Floppy not read | mechanism / belt | Clean / Gotek |
| Instability | caps | Recap |
| Dead keys | keyboard | Clean |
Modernisation & mods — what to buy, how¶
Modern storage
- FM77 (integrated drive): Gotek + FlashFloppy or HxC 🟡 → .d77 images from USB/SD.
- FM-7/8 (cassette): load via audio 🟢 from a PC/phone; disk interfaces + Gotek 🟡.
Video - RGB output 🟢 → SCART then OSSC / RetroTINK or RGB2HDMI (the FM77AV outputs an extended palette) for crisp digital.
Reliability - Recap 🟠; change drive belts (FM77); on a crash, isolate the main 6809 from the sub-CPU (dual 6809) during diagnosis.
⚠️ Do not host ROMs/games — method only.
See also¶
- FM Towns (the 32-bit successor) · Sharp X1/MZ · Tandy CoCo (same 6809) · Recap.
Sources & attribution¶
- Photo Fujitsu FM-New7 (série FM-7) — JCCyC, CC BY-SA 3.0, Wikimedia Commons — https://commons.wikimedia.org/wiki/File:FM-New7,_May_2013_B.jpg
- Wikipedia — FM-7 (dual 6809, YM2203, FM77AV) — CC-BY-SA — https://en.wikipedia.org/wiki/FM-7
- Established JP retro community knowledge (belts, recap) — synthesis.
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.
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