Atomiswave (also known as Sammy Atomiswave) is an arcade system board developed and used by Sammy (and later by Sega) for a variety of arcade releases from the years 2003 to 2006 (with some released in the late 2000's). It is based on Sega's NAOMI hardware, which itself shares the same architecture as Sega's Dreamcast console.
Despite being a cost-reduced version of the NAOMI (with the only real difference being half the VRAM amount), its main selling points include a smaller form-factor (with smaller ROM cartridges) and support for two expansion cartridges: one for I/O Expansion (allowing easy configuration with with light guns and driving controls) and one for Broadband Networks (allowing some games to support online leaderboards via the AW-Net service and for some games to support multi-cabinet multiplayer).
While it was primarily used for Sammy's series of racing and shooting games (such as Sports Shooting USA, Faster Than Speed, and Ranger Mission), the hardware was used as the base for some games by Arc System Works, SNK Playmore, and Dimps, as well as some releases by Sega themselves (most notably Sega Bass Fishing Challenge). Unlike games released for the NAOMI, all games for the Atomiswave were released on ROM cartridges only. While none of them received ports to the Dreamcast, and half of which did not receive any home port at all, some games have received unofficial Dreamcast conversions.
All games prior to the Sega and Sammy merger (from 2003 to sometime in 2005) were released by Sammy, while all games released thereafter were released by Sega.
Sammy / Sega
Arc System Works