Sega System 1/2


A system 1 board has been acquired in a working state for hardware testing and analysis. No hardware testing has been performed so far.


Refer to SegaRetro (System 1, System 2) and System16 (System 1, System 2) for a general hardware overview and list of games.

System Revisions

It’s worth noting first that I don’t believe the naming that’s currently applied to this hardware is correct. The terms “System 1” and “System 2” (and occasionally “System 8”), which are often used online seem entirely made up by the emulation community, with no markings on the boards themselves identifying them in this way, nor the game flyers or manuals, or the schematics. While it’s possible that Sega officially named this hardware retrospectively, which has known to have occurred for some later hardware platforms, the general information that’s commonly published providing system specifications for this hardware seems unsupported by actual references, and the division between System 1 and 2 games seems confusing and in some cases contradictory. The often quoted statement that the “System 2” added a ROM board is demonstratively false, with the circulated image to support this claim simply being the “Shooting Master” game, which added a daughter board by socketing various main board ICs from a 171-5303 board and relocating them onto the daughter board, with additional hardware for the gun interface.

One thing that is correct is that there is one significant hardware change which affects software compatibility, namely the addition of the “315-5049” tilemap hardware. Games that didn’t make use of this hardware can potentially run on any of the boards, possibly with adjustments to account for differences in supported ROM sizes and the like. A variety of official daughter boards were produced by Sega to make older board revisions compatible with newer games which required adjustments in these areas. With the use of these daughter boards, it’s likely any game could be adapted to run on any board, unless a dependency on the “315-5049” chip restricted them to “171-5303” board revisions. The best example of this is WonderBoy, which is documented in its manual, and can be seen from pictures, to be running across all the hardware from the earliest board revision to the latest one.

The following are the known board revisions to exist for System 1 hardware:

*171-5019 [1982 83020?] Super Locomotive *171-5034 [1983 830528] (Star Jacker - 8.JPG, WonderBoy - 51.JPG, Up n Down - 1.JPG) ?171-5054 [1983 831205] (Regulus - 2.JPG) ?171-5054-01 [1983 840516] (Regulus - 19.JPG) *171-5054-02 [1984 8406??] (Flicky - 1.JPG) ?171-5054-03 [1985 850419] (Choplifter - 52.JPG, My Hero - 10.JPG) *171-5303 [1985] (Choplifter - 42.JPG) *171-5303-01 [1985] (Choplifter - 12.JPG) *171-5303-02 [1985 860508] (Toki no Senshi - 1.JPG, WonderBoy - 23.JPG, WonderBoy - 40.JPG)

There are three major board variants, with five minor revisions across those lines. Note that the Wonder Boy dipswitch sheet suggests a 171-5154-01 boards existed, but this appears to be a misprint, with “5054” being the intended board number here.

There is not enough information currently available from the various online sources to clearly identify which games were released using which main boards, and the prevalence of conversion kits with daughter boards further complicates matters. With the large number of board revisions, and lack of overall system identity and branding however, it doesn’t appear that this was originally intended to be used as a formal general purpose hardware platform. The fact that Star Jacker, the first game to be released on a shared board for this system, had the game number silkscreened on the PCB, supports this.

It seems clear that there’s no distinct System 1 and System 2 hardware platforms, although there is a case to be made that all the various games released with similar and largely compatible hardware form a de-facto system of sorts. It appears likely that one first game was produced with a game-specific main board. To save time and costs however, that board was then re-used for other games. In some cases the board was used in an identical form, but in other cases the main board was revised to extend it slightly, for example to allow larger ROM sizes, or to add additional hardware, but still in a game-specific form. This approach had served Sega well in the past, no doubt reducing the up-front development time and costs for the first title, but with 30+ games released for this line of hardware, more than Sega had ever done before on an arcade platform, this approach would have ended up quite inefficient over time. It appears Sega ultimately found themselves revising the hardware once for approximately every three games they released. It seems highly likely that Sega’s experience with this hardware is what lead them to build formal general purpose platforms shortly afterwards. Having a flexible and extensible general purpose base board, with a switchable ROM board, allowed Sega to release many titles on a single hardware platform, reducing R&D costs over the life of the system and simplifying software development, while also making it easier for arcade operators to upgrade to new titles on the same platform.


       Code        Document Author Description Source
  Choplifter Schematics Sega Complete hardware schematics for Choplifter running on a 171-5303 main board. These are the original schematics from Sega. The schematics are clean, however slightly lower resolution than would be ideal. Some of the smaller labels are a bit hard to make out.
420-5110 Star Jacker Service Manual Sega Full service manual for StarJacker, including the board layout and schematics for the 171-5034 main board.
420-5270-91 Choplifter Instruction Manual Sega Choplifter conversion kit manual, with wiring diagram. 171-5303 or 171-5054-03 main board.
420-5295 Wonder Boy Instruction Manual Sega Wonder Boy conversion kit manual, with wiring diagram. 171-5034, 171-5054, 171-5054-01, 171-5054-02, 171-5054-03, or 171-5303-02 main board.
421-6057 Heavy Metal Dipswitch and Pinout Sega Heavy Metal dipswitch settings and pinout. 171-5303 or 171-5054-03 main board.
421-6113 My Hero Dipswitch and Pinout Sega My Hero dipswitch settings and pinout. 171-5034, 171-5054, 171-5054-01, 171-5054-02, or 171-5054-03 main board.
421-6178 Choplifter Dipswitch and Pinout Sega Choplifter dipswitch settings and pinout. 171-5303 or 171-5054-03 main board.
421-6285 Rafflesia Dipswitch and Pinout Sega Rafflesia dipswitch settings and pinout. 171-5034, 171-5054, 171-5054-01, 171-5054-02, or 171-5054-03 main board.
421-6307 Wonder Boy Dipswitch and Pinout Sega Wonder Boy dipswitch settings and pinout. 171-5034, 171-5054, 171-5054-01, 171-5054-02, 171-5054-03, or 171-5303-02 main board.
421-7289 UFO Senshi Yohko Chan Dipswitch and Pinout Sega UFO Senshi Yohko Chan dipswitch settings and pinout. 171-5303, 171-5303-01, or 171-5303-02 main board.
CN-112 Flicky Dipswitch and Pinout   Flicky dipswitch settings and pinout. Unofficial third party sheet.
  Wonder Boy II Dipswitch and Pinout   Wonder Boy II dipswitch settings and pinout. Unofficial third party sheet.
28-081300 Regulus Conversion Kit Technical Manual Wico Brief third party conversion kit instructions for Regulus.

High Resolution Photos


Miscellaneous Photos

Here’s a collection of images of this system that have been posted online from various sources: Hardware Photos