Boot ROM

The Basic Input-Output System or BIOS is computer interface code that locates and loads the operating system into RAM. It provides low-level communication, operation and configuration to the hardware of a system, which at a minimum drives the joypad and provides primitive output to a display. The BIOS is usually written in the Assembly language native to the processor. Listed below is information regarding the attraction modes to Sega's hardware systems, which are the sequences displayed to the end user upon starting up the system.

Sega Master System

Based on the Sega Mark III in Japan, the Sega Master System (SMS) had a BIOS just like any other computer interface. Almost all of Sega's hardware systems had some form startup sequence that graphically told the end user that a game was loaded and ready to play. However, what was unique about SMS was that Sega had included built-in games that could be played without any cartridges inserted.

The first known BIOS released was based upon the Sega Mark III, which featured an animated blue SEGA logo, along with MASTER SYSTEM written underneath. This was a prototype that wasn't released in the final product and is designated as Prototype M404 among emulation communities. (See here for video demonstration)

Among its final release in North America in June 1986, the first major BIOS known publicly is the SEGA startup sequence. The animation sequence this time was the SEGA logo sliding from the left side in the center of the screen, followed by MASTER SYSTEM and its copyright information shown underneath. The trademark SEGA sound as heard in many of the Sonic the Hedgehog games, is also played in the background using melodic system tones (See here). Although less animated, there was an extra hidden game that could played upon startup. By pressing 1, 2 and UP on the controller, the player could play the infamous Snail game.

Japanese releases of the SMS BIOS offered more musical graphical enhancements, along with music from Space Harrier (See here).

Finally, Sega also packaged other games with the system built-in similar to the Snail game, but was no longer hidden to the end user. Depending on the console build and BIOS included with the system, players could choose to play either Hang On, Missile Defense 3-D, and Safari Hunt.

Sega Mega Drive / Genesis

The Sega Mega Drive (MD) did not truly include a BIOS startup sequence as extravagant as the Sega Master System, but a BIOS was included to give the MD instructions of what to load for the game. Upon startup, the MD checks a number of things, but most importantly, the region of the game, its checksum, and headers related to the copyright. Without these features, the game would then be "locked-out" of region and could not be played on the system. For example, users could not play a Japanese region cartridge in a North American system.

North American audiences had three different release models of the MD, known as the Sega Genesis. All three had the same startup sequence, which on the screen would read "PRODUCED BY DR | UNDER LICENSE FROM | SEGA ENTERPRISES LTD." with | representing a line break on the white-on-black screen. With this shown on the screen, the game could then continue loading its sequences. Although not advertised, the Genesis 3 model, produced by Majestic, allowed users to play all games from any region, as the cartridge slot could fit any cartridge.

Sega Mega-CD

The Sega Mega CD, known as the Sega CD in North American audiences, featured a BIOS similar to that of the Sega Master System. Its size was 1-Megabit and was primarily used for playing Sega-CD games, audio compact discs, and its access time was relatively about 800 milliseconds long. There were multiple BIOS releases based upon the model of the CD system and among different countries.

First and foremost, the Mega-CD was not a standalone system. It was actually attached to any Model 1 or 2 Sega Mega Drive, giving the Mega Drive full control of the CD system. The standalone Multi-Mega and CDX systems, although combined as one machine, follow the same startup procedures as follows. If a cartridge based game is inserted into the MD, then the MCD remains idle. However, if there is no cartridge inserted, then the MCD gets full control and begins its sequences. If no CD is inserted, the attract music and SEGA animations continue to play until the player makes a decision. He or she can either continue watching the sequence, insert a game disc, or press A, B, or C to enter the CD-Player mode. From the CD Player, the user can either play music, manage items on the backup RAM, or again, insert a game disc.

Below are revisions of each BIOS version according to region and model. Clicking on the region will link you to a video demonstration of its attract mode. For CRC information, downloading of BIOS files, and further machines that feature the BIOS below, please see the BIOS section from the Sega Mega CD page.

BIOS Revisions

Version	System & Region
1.00	Mega-CD (E/J))
1.10	Sega CD (NA)
2.00	Mega-CD 2 (E/J), Sega CD 2 (NA)
2.11	Mega-CD 2 (E/J), Sega CD 2 (NA)
2.21	Sega Multi-Mega (E), Sega Genesis CDX (NA)

If inserted, a Mega Mouse can control the arrow on screen during the CD Player mode rather than moving around with a control pad. This feature is only enabled on Model 2 Mega-CD systems.

Information relating to Sega Saturn and Sega Dreamcast are coming soon!

Screenshots

http://www.emulationgalaxy.co.yu/images/systems/SATURN_bios.jpg Sega Saturn BIOS.