The Functionality of the Sega Dreamcast

Popular Science magazine justifiably named the Sega Dreamcast one of the most influential and innovative products of 1999. With impressive specs, outstanding games, and a creative ad campaign, it was the latest groundbreaking system from Sega, a company famous for revolutionizing video game technology.

In this edition of Mytour, explore this amazing system, its revolutionary controller, and Sega's unique optical storage technology. You'll also learn about the VMS, a multifunctional device that can stand on its own!

Dreamcast History

Sega, a dominant force in arcades, entered the home console market shortly after Nintendo. The Sega Master System, known as the Mark III in Japan, was launched in the United States in 1986. This system featured an 8-bit CPU, 128K ROM-based operating system, and 128K of RAM. It supported two types of cartridges: a larger one that could store one megabit of game code and a smaller one with 256 kilobits.

In 1989, Sega introduced the first 16-bit home console, the Genesis, powered by Motorola's 68000 processor. The system was technically ahead of its time, but its success was eclipsed by the launch of Nintendo's Super Nintendo Entertainment System later that year.

Sega beat both Sony and Nintendo to market with a 32-bit console, the Saturn, which debuted on May 11, 1995. This system featured dual 28.8 MHz 32-bit Hitachi SH-2 processors working in parallel. Despite its cutting-edge architecture, the Saturn quickly fell behind in the race, overshadowed by Sony's PlayStation.

Code-named Katana, the Dreamcast was released in late 1999, becoming the first console to offer a built-in modem and 128-bit graphics.

Dreamcast Console Overview

Let’s dive into the inner workings of the Dreamcast and explore the potential of its components:

Processor: 64-bit Hitachi SH-4

Processor: 64-bit Hitachi SH-4

Graphics: 128-bit 100 MHz NEC PowerVR 2DC

Geometry Engine:

Audio: 45 MHz Yamaha Super Intelligent sound processor

Memory: 16 MB

Operating System: Windows CE-based or custom Sega OS

Game Medium: Proprietary GD-ROM (Gigabyte Disc)

Modem: 56 kilobits per second (Kbps)

The Dreamcast made history as the first console to feature a built-in 56 Kbps modem. This addition was designed to support online gameplay over a phone line, allowing players to engage in matches over long distances. Sega also developed an external cable or DSL modem, with broadband networks in the works to enable faster online gaming on the Dreamcast.

Dreamcast Processor

Like the N64 and the PlayStation, the Dreamcast is equipped with a RISC processor, which stands for reduced instruction set computer. This means the processor handles a smaller set of simpler instructions, making it more efficient. RISC processors are also superscalar, meaning they can execute multiple instructions at the same time. This combination of efficiency and speed allows the Dreamcast CPU to outperform other chips with faster clock speeds.

To reduce production costs, the graphics processor and system control circuitry are integrated into a single application specific integrated circuit (ASIC). In simple terms, this means a custom chip is designed to manage all the essential functions that would usually require separate chips. The Dreamcast sound processor is another example of an ASIC, combining a 45 MHz ARM7 CPU with a Yamaha digital signal processor (DSP). The ARM7 is a 32-bit RISC chip that processes compressed adaptive differential pulse code modulation (ADPCM) audio in real time. ADPCM is used to sample analog signals, compress them at a ratio of 4:1, and store them in a digital format.

The Dreamcast is equipped with several hardware effects powered by the PowerVR chip, such as alpha blending, perspective correction, and mip mapping.

Alpha blending leverages the alpha channel to add transparency effects to objects. This graphics technique is widely used in digital video, animation, and video games to create special visual effects. It works by allocating 24 bits to define the red, green, and blue components (8 bits each) to form a specific color. An additional 8 bits define a grayscale mask, which controls the level of transparency. The darker the gray in the alpha channel, the more transparent the object becomes. By manipulating the gray areas of the mask, one can generate fog, water effects, or even subtle transparency in objects.

Mip mapping is a fascinating technique used in texture mapping, where multiple versions of each texture map are created at different sizes. Essentially, the system replaces a distant object's texture with a more detailed version as the player gets closer. Here's how Dreamcast applies this process with trilinear mip mapping:

When a game is inserted into the Dreamcast console, the following sequence occurs:

The Dreamcast was the first console to feature a built-in 56 Kbps modem, enabling online play over a standard phone line. This allowed users to connect and compete in games over long distances. In addition to the internal modem, Sega is developing an external cable or DSL modem, with broadband networks being developed to support faster online gaming for Dreamcast users.

Dreamcast Controller

Similar to other gaming systems, the controller serves as the main interface for the Dreamcast. The standard Dreamcast controller is equipped with 11 buttons and an analog joystick. The buttons consist of:

Each button can be customized to trigger a unique action, but all buttons, excluding the two analog triggers and joystick, operate similarly. Essentially, each button acts as a switch that completes a circuit when pressed. A metal disk beneath the button makes contact with two conductive strips on the controller’s circuit board. When this contact is made, the electricity flows between the strips. The controller detects this and sends the data to the Dreamcast. The CPU then compares the data with the game’s programming and activates the corresponding action. Similarly, there’s a metal disk under each arm of the directional pad. If pressing down on the pad makes the character crouch in a game, this interaction triggers a sequence that leads to the crouching action.

The analog joystick and triggers function very differently from the regular buttons. Each trigger has a small magnet attached to its arm. When the trigger is pressed, the magnet moves toward a sensor on the controller’s circuit board. This action, known as induction, causes the magnet to alter the current passing through the sensor. A foam layer beneath the magnet compresses as the trigger is pushed, bringing the magnet closer to the sensor. The proximity of the magnet increases resistance, making the triggers pressure-sensitive!

The joystick also uses a magnet paired with four small sensors placed like the points of a compass—north, south, east, and west. The joystick's base is shaped like a ball with tiny spokes, sitting in a socket above the sensors. The socket’s spikes fit into the ball’s spokes, preventing the joystick from twisting out of alignment with the sensors. As the joystick is moved, the magnet inside it adjusts its position relative to the sensors. The system measures the changes in induction caused by the magnet’s movement to determine the joystick’s position.

The controller is equipped with two expansion ports that can accommodate devices such as memory cards, tremor packs, Visual Memory System (VMS) devices, and various other system accessories.

A popular choice is the tremor pack, which delivers force feedback. This function adds a physical sensation to specific actions within a game. For instance, in a racing game, you might experience a sudden jolt as your car crashes into a wall. The force feedback works via a simple electric motor, where an unbalanced weight is mounted on the motor’s shaft. When powered on, the motor spins the weight, causing the motor to wobble. Since the motor is securely attached inside the tremor pack, this wobble translates into a vibrating sensation in the controller.

While the Dreamcast supports standard memory cards, the VMS units are exclusive to this console. The VMS is essentially a miniature Personal Digital Assistant (PDA) that fits into the controller’s upper expansion port.

Each VMS unit is approximately the size of a business card and includes the following features:

When inserted into the Dreamcast controller, the VMS’s LCD display unlocks a range of unique features. For example, during a football game, you can secretly select plays without your opponent seeing your choices. Besides functioning as a memory card for the Dreamcast, the VMS can also be used independently. You can download small games and traditional PDA tools like a calendar and phone book, and take them with you.

Dreamcast Games

Although Dreamcast games share similarities with CD-ROMs, the optical disc used is unique to the system and can store up to 1.2 gigabytes of data. This offers ample space, though most games only utilize a portion of it for the game itself. What consumes much of this storage are the impressive full-motion video sequences that appear as intros and intermissions in many Dreamcast games.

Unlike cartridge-based games, there is a noticeable delay when loading a game from the CD. However, this delay is the trade-off for faster loading times, as cartridges offer significantly less storage. Most Dreamcast games operate on a customized version of Microsoft Windows CE, though some use Sega’s proprietary Dreamcast operating system.

Like regular CDs, Dreamcast game discs are vulnerable to scratches and extreme heat. In fact, they're even more sensitive, as a single scratch on a game CD can render it completely unplayable.

The Dreamcast boasts a wide array of games that span all genres, with its library expanding rapidly. Game prices vary, starting from under $20 for pre-owned titles to over $75 for some of the most sought-after new releases.