MultiROM - The LaserCon ALG MultiROM is a direct replacement for the
original RAM/ROM board used in American Laser Games arcade cabinets. With this board, you can choose from Mad Dog McCree,
Mad Dog II, Who Shot Johnny Rock?, Gallagher's Gallery, Space Pirates, Crime Patrol, Crime Patrol 2,
and The Last Bounty Hunter. Simply change the disc, turn a dial, and you're playing a new game
(laserdiscs not included).
Different Versions - Three different versions of these arcade games exist. The first two use laserdisc technology, and the third is based
on a 3DO home console. Early systems were made for one player only and use a plain Amiga 500 motherboard, a genlock, a Sony
LDP-1450 laserdisc player, a Rev. A RAM/ROM board, a sound amplifier board, a
single-player optoisolator board, and a light gun. When two-player
games were developed, a partial redesign of the existing hardware was done. The RAM/ROM board was upgraded to Rev. B. The optoisolator board
was expanded to accept a second gun as input, and the sound amplifier board was integrated into it. The two boards combined were named the
TAOS board. A one-player game can be run on a two-player
setup by using the proper RAM/ROM board and utilizing the second player gun as the only gun for shooting.
Later versions were built around a Panasonic 3DO system, thus based on CD-ROM technology. The 3DO systems
were slightly modified for use in arcade games, utilizing a custom interface (Coyote board) to connect to the guns, coin mechs, and control panel
inputs. An example of a modification that was done is the spindle motor replacement. Regular 3DO spindle motors were not designed to run all
day in an arcade environment and were failing soon, so Panasonic replaced them with heavy-duty ones. The
gameplay is pretty much the same as the laserdisc versions, but the video quality is inferior. The arcade game
CD-ROMs are different from the home consumer versions, and they are not interchangeable.
All versions of the games, both American and European, run on the NTSC video format. The genlock and/or 3DO video outputs are NTSC composite, so
the games can be played on a regular NTSC TV or monitor with composite video input. However, for arcade use, a standard NTSC demodulator board is
used to display the NTSC video on the arcade monitors (25" and 33" versions). The big screen models use a regular 46"
retro-projection Pioneer TV mounted inside the cabinet.
Gun Info - For info on the gun wiring, check the ALG Gun Wiring Diagram. Most of the guns were black
metal. Early models needed an external 'shot amplifier module' between the gun and the optoisolator board. This module was later
removed/replaced with a hardware upgrade of the PCB mounted inside the gun itself.
Most of the weapons use a mercury switch installed inside their shell to detect the gun position (horizontal = shooting ; vertical = gun folded, reload
position). Who Shot Johnny Rock? uses a small machine gun without a mercury switch (the game doesn't support
reloading). Space Pirates uses a sort of space laser gun. The 3DO guns are orange plastic guns. Similar guns of the same color were
sometimes also used in the laserdisc versions of the games. The guns were lighter, with the same hardware as the metal guns, but mounted inside a
gun shell marked 'Nintendo'.
Interchangeability - Most of the games are interchangeable with minor hardware adjustments; however, Fast Draw Showdown uses a vertically
mounted monitor, and all the other games are horizontal. To change games, you basically have to change the RAM/ROM board and the laserdisc. The
laserdiscs were all manufactured by 3M, single-sided, and plastic-backed,
with audio in English and dubbed in many other languages such as Spanish, French, Italian, Chinese, and Japanese.
RAM / ROM Board - There are two types of RAM/ROM boards. Rev. A, the early version, uses two 27512 EPROMs (64 kB each), and Rev. B uses
two 27C1001 or 27C010 EPROMs (128 kB each). In addition to the two EPROMs (U1, U2) which contain the game code, each RAM/ROM board is equipped
with a zeropower RAM (U3 - MK48Z028-20 or equiv.) and two PAL chips (U4, U5 - PAL16L8). The idea of the
PALs was to scramble the address lines and the PAL IC surfaces were scraped to prevent illegal reproduction of the boards. Other than that, the
software on the EPROMs isn't encrypted at all, just scrambled in the addresses. Mad Dog McCree has its own scramble (Rev. A), and
Who Shot Johnny Rock? has its own (Rev. A), but the other games (Rev. B) were all the same. It was too much trouble to keep coming up
with additional board versions. Each game could run on the same RAM/ROM board; however, for production, they were run through different programs to
scramble the bits. For more info on this, visit the ALG RAM/ROM Info page.
PAL Chip Workarounds - Some of the PAL chips mentioned above are more rare than others, which can make it difficult to swap/share the same RAM/ROM
board between different games. The following ROM modifications: Space Pirates 1.4b and
Who Shot Johnny Rock? 1.6a and 1.6b (available in the ROM table above) were made to alleviate this problem and make these
games compatible with the more common PAL chips.
Mad Dog McCree and Who Shot Johnny Rock? were the first games to be
developed. They were designed as single-player games only. The
two-player games require more ROM space because of the amount of software, so a Rev. B of the RAM/ROM board
with larger-sized EPROMs was produced.
- 
