It's still thinking!
The Sega Dreamcast was Sega's final home video game console created during the 6th Video Game Generation, "developed primarily to detoxify the Sega brand and rekindle the trust and market success seen in the days of the [Sega Genesis]"(1). Launched on 09/09/1999 in the United States (before the Sony Playstation 2, the Nintendo GameCube, and Microsoft's original XBox), the Sega Dreamcast was innovative and ahead of its time.
It was the first home video gaming console to have online support out-of-the-box via its 56k dial-up modem that came with it. This modem would allow people to browse the web via custom web browsers on discs such as PlanetWeb and to connect certain games for online multiplayer, such as Quake III Arena, Starlancer, 4x4 Evo, and many more titles. The modem could be upgraded to a Broadband Adapter (BBA) for a higher speed, larger bandwidth DSL internet connection; however, these units are rare, in high-demand, and expensive (even today on eBay). The system also had 4 controller ports on the front for multiplayer games (similar to the Nintendo 64), and had 2 controller port slots on the controllers. The slots on the controllers allow one to insert accessories such as a VMU (Visual Memory Unit) memory card, which stores game saves. The VMU has a small dot-matrix display on the front (like with Ti-84 graphing calculators), to allow one to play mini games or for games to display pictures on, and could produce simple PSG tones.
Sega Dreamcast specs:
RISC Hitach SH-4
Superscalar opcode execution
Custom Yamaha AICA sound chip
ARM7-based 32-bit processor
Produces up to 64 (AD)PCM sound channels
16MB of RAM
12x speed GD-ROM Drive
"GD" stands for "Gigadisc"
Custom disc format created by both Yamaha and Sega
Holds approximately 1.0 GB of data
Compared to ~700MB on a standard CD-ROM
Operating systems could be bundled on the discs for the games to utilize
Sega's own Katana OS
Dreamcast-compatible Windows CE OS
Despite the Dreamcast selling okay in various parts of the world, in 2001, faced with significant competition by the upcoming Sony PlayStation 2 and its other rivals, Sega cancelled the Dreamcast console prematurely and left the industry as a 1st-party developer creating new consoles for the home video game console market. Today, Sega primarily focuses on creating software as a 3rd-party developer, but does still create new Sega arcade hardware.
Although the Dreamcast had a short official life span, the Dreamcast is alive and "still thinking" today by its massive homebrew community, and still has commercial titles coming out for it, such as DUx. Today, a homebrew-developed KalistiOS OS has been created for homebrew to utilize, as well as DreamShell for SDISO read/write access for files. There are also modern ways to get a DC back online to play on unofficial, reversed-engineered servers, including setting up a DC-PC server, or utilizing a DreamPi.
Furthermore, the system has many ways to run unsigned code on it, including:
Burning MIL-CD compatible CD-Rs
Run SDISOs with certain hardware
Hooking up an IDE HDD with some electronics hacking
BBA-Coder's cable (need a rare BBA Adapter, and is slow)
Although the Dreamcast officially and sadly was cancelled prematurely by Sega in 2001, the Dreamcast is a very powerful machine with various ways to run and create homebrew software for it.
1. Source: http://segaretro.org/Sega_Dreamcast
Shown in the subpages below are various Dreamcast related tools and homebrew