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SNK Neo Geo CD

The CD-ROM version of the Neo Geo (1994). Same hardware as the AES but with games at ~$50 instead of ~$300 on cartridge. The catch: a single-speed drive with legendary loading times, partly fixed by the CDZ model (double-speed).

SNK Neo Geo CD
SNK Neo Geo CD, front-loading model (1994). Photo: Evan-Amos, Wikimedia Commons, public domain.

Identification

Field Value
Manufacturer SNK
Release 1994 (JP), 1994 (EU), 1996 (US)
Generation 4th (Neo Geo, 2D)
Models Front-loader (JP) · Top-loader (worldwide) · CDZ (JP, faster)
Media CD-ROM

Architecture

The Neo Geo CD uses the same architecture as the AES/MVS: the CD merely replaces the cartridge with a cheap medium. Data is loaded into RAM before play (hence the loading times).

Block Chip Clock Role
CPU Motorola 68000 12 MHz same core as the AES
Sound (CPU) Zilog Z80 4 MHz drives the sound
Sound (chip) Yamaha YM2610 ADPCM + FM (identical to the arcade)
Memory 7 MB RAM total 2 MB program + 4 MB graphics + 1 MB sound + fix/VRAM
Media CD-ROM drive single-speed (double-speed on CDZ)

The 7 MB of RAM matches the capacity of a large MVS cartridge: the game is copied entirely into memory, which avoids in-game loading… but forces long loads between stages/rounds.

Models & loading

  • Front-loader (1994, Japan, ~25,000 units): motorised front loading.
  • Top-loader (worldwide distribution): top loading, the most common.
  • CDZ (late 1995, Japan): double-speed drive — much shorter loads, the model to favour for actual play.
  • Loading times: roughly 30–60 s depending on the game on single-speed models — the machine's main criticism.

Region & saves

  • No hard region lock, but the console is "region aware": some games' language follows the BIOS territory setting (Japan/US/Europe).
  • Saves: internal backup memory + a memory card slot compatible with the Neo Geo ecosystem (AES/MVS).

Controllers & games

  • Controller: Neo Geo CD pad (D-pad + buttons), in the spirit of the AES stick.
  • Library: SNK's hits (Metal Slug, The King of Fighters, Samurai Shodown, Fatal Fury, Garou…) made affordable — the selling point against the prohibitive price of AES cartridges.

Common faults

Symptom Likely cause Lead
Won't read CDs / random reads Worn laser / optical block Adjust/replace, or ODE (image it first)
Loading/tray dead Belt / mechanism Replace belt, clean the rail
Degraded sound/video, corrosion Capacitors (electrolytics) Targeted recap
Lost saves Flat backup battery Replace the battery
No image Power, contacts Base diagnosis

Preservation & emulation

  • ODE / CD imaging: image the discs while they still read; ODE to escape the ageing laser.
  • Emulation: mature Neo Geo cores (MAME, FinalBurn Neo) that faithfully reproduce the YM2610 and the 68000.

Video output: the missing composite sync ✅

All Neo Geo CD consoles ship WITHOUT composite sync (CSYNC) on the AV out port

This is a quirk of the machine, not a fault. In practice it is generally not a problem: modern equipment — HD Retrovision cables, the RetroTINK line of scalers — accept composite video as sync without real issue. (Source: ConsoleMods, CC-BY-SA.)

The documented "CSYNC mod" DOES NOT WORK — know this before reaching for the iron

ConsoleMods documents a CSYNC restoration procedure while explicitly stating that it does not work:

  • CRTs are unable to sync to the resulting image;
  • modern upscalers do not work with it either;
  • even LM1881 boards cannot strip the sync correctly from the composite video.

The reasons have not been investigated to date. We keep the procedure below as documentary preservation, not as a recommendation.

✅ What does work, on the other hand: the "Sync on Luma" mod.

Documented CSYNC procedure (non-functional — archived for the record)

⚠️ This mod requires cutting several traces and should only be attempted at one's own risk — all the more so as it does not succeed.

Tools: Phillips screwdriver, soldering iron, leaded solder, wire, wire cutters and stripper, multimeter, razor blade / X-Acto knife.

Important technical point: sync is pulled directly from the CXA1645P video encoder, which is TTL sync. Running it through an Extron or another device capable of accepting TTL sync is fine, but ⚠️ never connect direct TTL sync to equipment such as an RGB monitor. Adding a 680 ohm resistor to the device or cable lowers the sync voltage to an acceptable level. It is also possible to use luma from the S-Video connector as the sync source instead of the encoder's TTL sync.

  1. Disassemble the console. With the top cover removed, unscrew the circuit board carrying the output connectors and flip it over — the wires do not need to be removed.
  2. Locate the multi-out connector. The composite video pin is wired directly to the composite sync pin and then to the composite video output. Use a multimeter to verify that the three pins concerned are indeed connected.
  3. With a razor blade, cut the traces before and after the composite sync pin of the DIN jack. Verify with a multimeter that there is no longer continuity between the composite sync pin and those traces.
  4. Add two wires: the first returns the composite video line from the CXA1645 to the composite video pin of the multi-out (and hence also to the actual composite video output connector, since they remain linked); the second connects pin 10 (sync input) of the encoder to pin 7 on the multi-out.
  5. Test, then reassemble.

Mods & repair — what to buy, how

Loading times: the Achilles' heel

The front-loader / top-loader read at 1× → very long loads (the CD RAM is small and reloaded often). The CDZ reads at 2× and loads much faster — prefer a CDZ for playing, or move to an ODE.

  • ODE (drive emulator) 🟡: a community ODE replaces the laser/belt block and loads from SD → removes the mechanical failure and sharply cuts loading times. Installs via the drive connector/flex. → ODE mods.
  • Laser / belt service 🟡: if keeping the stock drive — replace the belt (it dries out, tray/loading fails), clean the lens and adjust laser gain; image the discs first.
  • Targeted recap: aging power/audio electrolytics (degraded sound/video, corrosion).
  • Region: the lock lives in the BIOS → region-free BIOS (reprogrammed chip) removes it on socketed-BIOS models.
  • Backup battery: check/replace (internal memory) → backup batteries.

Photos / assets

(To add: Neo Geo CD top-loader, CDZ, laser block, board.)

Advanced repair

Optical drive (belt/laser = a notorious weak point, slow drives) + recap. Methods: ODE (optical drive) · Recap · PCB fault-finding.

Sources & attribution

  • ConsoleMods Wiki — Neo Geo CD CSYNC Mod — CC-BY-SA — no composite sync from the factory on any Neo Geo CD, the source's own warning that the CSYNC mod does not work (CRTs, upscalers and LM1881 all fail), the Sync on Luma mod does work, CXA1645P TTL sync and the 680 ohm resistor — https://consolemods.org/wiki/Neo_Geo:Neo_Geo_CD_CSYNC_Mod

What we did not transcribe (and why)

On the Neo Geo CD side, the ConsoleMods pages Power Supply Fuse (Neo Geo CD) and Adjusting CD Laser are empty to this day (red links): our laser adjustment and belt sections therefore rest on our existing sources, with nothing invented.

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.