The Sony PlayStation 2 (PS2) was one of the most anticipated products of 2001. The technical features of the PS2 are very impressive.
In this edition of HowStuffWorks, you will learn about the development of the PS2, what's inside the box and how it all works together. You will also learn about the controller and the games!
In 1988, Sony entered into an agreement with Nintendo to develop a CD-ROM attachment, known as the Super Disc, for the soon-to-be released Super Nintendo. Due to many contractual and licensing problems, the Super Disc was never released. Instead, a modified version was introduced by Sony in 1991, as part of a system called the Play Station.
The Play Station read Super Discs, special interactive CDs based on technology developed by Sony and Phillips called CD-ROM/XA. This extension of the CD-ROM format allowed audio, video and computer data to be accessed simultaneously by the processor. The Play Station also read audio CDs and had a cartridge port for accepting Super Nintendo game cartridges. The original Play Station was envisioned as the core of a home multimedia center. Sony only manufactured about 200 of them before deciding to retool the design.
The new design, dubbed the PlayStation X, or PSX, dropped the Super Nintendo cartridge port and focused solely on CD-ROM-based games. The component hardware inside the console was revamped as well to ensure an immersing and responsive gaming experience. Launched in Japan in December of 1994, and in the United States and Europe in September of 1995, the PlayStation quickly became the most popular system available.
Let's take a look at the components inside a PlayStation 2 console, and what their capabilities are. (Check out How Video Game Systems Work first for a general introduction to game consoles.)
Processor: 128-bit "Emotion Engine"
- Processor clock speed: 300 MHz
- Floating point unit (FPU) co-processor operating at 6.2 gigaflops
- Bus speed: 3.2 GB per second
- Original Play Station CPU core as I/O processor
Graphics: "Graphics Synthesizer"
- 150 MHz
- Embedded cache
- 4 MB VRAM
- Resolution: 640x480 or 320x240 interlaced
- Colors: 24-bit (16,777,216) maximum, as well as 16-bit (65,536) mode
- Geometry engine:alpha channel, anti-aliasing, Bezier surfacing, Gouraud shading, Mip mapping, perspective correction, Z-buffer
- Polygon rendering: 75 million polygons per second
Audio: SPU2 (+CPU)
- Channels: 48
- Sample rate: 44.1 KHz or 48 KHz
- Memory: 2 MB RAM
- Optical digital output
- Supports original PlayStation CDs
- Video DVD support
- Audio CD support
Like the original PlayStation, the CPU in the PS2 is a RISC processor. RISC stands for reduced instruction set computer, and means that the instructions and computations performed by the processor are simpler and fewer. Also, RISC chips are superscalar -- they can perform multiple instructions at the same time. This combination of capabilities, performing multiple instructions simultaneously and completing each instruction faster because it is simpler, allows the CPU to perform better than many chips with a much faster clock speed.
The floating point unit (FPU) is a special processor that is dedicated to handling complex mathematical equations, particularly those that include non-integers, numbers after the decimal point. These calculations are commonly referred to as floating point operations because the decimal point can move, or float, depending on the outcome of the calculation. The complexity of such numbers can create a tremendous bottleneck if the main processor has to take the time to perform each calculation. To alleviate this, the non-integer numbers are sent to the FPU.
The speed with which the FPU can process these calculations is expressed as floating point operations per second (FLOPS). A gigaflop is one billion of these. So the PS2's 6.2-gigaflop FPU can perform 6.2 billion floating point operations in a second!
The PS2 has several hardware effects that are handled by the Graphics Synthesizer. They include an alpha channel, Bezier surfacing, perspective correction and mip mapping.
The PS2 uses the alpha channel to add transparency effects to an object. This is a special graphics mode used by digital video, animation and video games to achieve certain looks.
- 24 bits are used to define the amounts of red, green and blue, 8 bits each, needed to create a specific color.
- Another 8 bits are used to create a gray-scale mask that acts as a separate layer for representing levels of object transparency.
- The degree of transparency is determined by how dark the gray in the alpha channel is.
- By making an area of the mask dark gray, you can make an object appear to be very transparent
- By making it light grey, you can create special fog or water effects.
Bezier surfacing is a 3-D modeling process that calculates how many polygons are needed to create an object. It bases the number on the level of detail necessary to make the object appear to be smooth to the viewer. The PS2 only performs these calculations on Bezier-surfaced objects that are in the game. Perspective correction makes the texture map resize at the same rate as the object that it is mapped on.
Mip mapping is a cool process. It is a form of texture mapping whereby different sizes of each texture map are made. In essence, the processor replaces the appearance of an object with a more detailed image as you move closer to the object in the game. Let's take a look at how the PS2 uses these maps in trilinear mip mapping:
- The system calculates the distance from your viewpoint to an object in the game.
- The system loads the texture maps for the object. Our three maps will be 64x64 (large), 32x32 (medium), and 8x8 (small).
- The system determines the exact size that the image map needs to be -- let's say 16x16 for our example here.
- Based on the size, it decides which two texture maps to use. For our example, it might choose the medium and small texture maps.
- It then interpolates (averages) between the two texture maps, creating a custom texture map that is 16x16, which it then applies to the object.
The goal is to use the smallest texture map possible given the distance that the object is from the viewer. The smaller the texture map, the lower the processing load. On nearby objects, however, small texture maps create a grainy surface that looks bad, so larger texture maps are used there.
The controller is the primary user interface for the PlayStation 2. With its winged shape, analog controls and abundance of well-positioned buttons, it is easy to use yet powerful.
The standard PS2 controller has 15 buttons; all of them, except for Analog, Start and Select are analog. They include:
- four buttons arranged as a directional pad on the top left
- Analog, Start and Select buttons in the top middle
- four action buttons on the top right
- two action buttons on the front left
- two action buttons on the front right
- one analog joystick on the top left
- one analog joystick on the top right
Although each button can be configured to perform a specific and distinctive action, they all work on the same principle. Each button has a tiny curved disk attached to its bottom. This disk is very conductive. When the button is depressed, the disk is pushed against a thin conductive strip mounted on the controller's circuit board. If the button is pressed lightly, the bottom part of the curved disk is all that touches the strip, increasing the level of conductivity slightly. As the button is pressed harder, more of the disk comes into contact with the strip, gradually increasing the level of conductivity. This varying degree of conductivity makes the buttons pressure-sensitive!
PS2 controllers also have two analog joysticks. These joysticks work in a completely different way from the buttons described above. Two potentiometers, variable resistors, are positioned at right angles to each other below the joystick. Current flows constantly through each one, but the amount of current is determined by the amount of resistance. Resistance is increased or decreased based on the position of the joystick. By monitoring the output of each potentiometer, the PS2 can determine the exact angle at which the joystick is being held, and trigger the appropriate response. In games that support them, analog features such as these allow for amazing control over gameplay.
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Another feature of the Dual Shock 2 controller, actually the reason for its name, is force feedback. This feature provides a tactile stimulation to certain actions in a game. For example, in a racing game, you might feel a jarring vibration as your car slams into the wall.
Force feedback is actually accomplished through the use of a very common device, a simple electric motor. In the Dual Shock 2 controller, two motors are used, one housed in each handgrip. The shaft of each motor holds an unbalanced weight. When power is supplied to the motor, it spins the weight. Because the weight is unbalanced, the motor tries to wobble. But since the motor is securely mounted inside the controller, the wobble translates into a shuddering vibration of the controller itself.
The CDs are just as susceptible to scratches and intense heat as regular audio CDs -- even more so in fact, since a scratch on a game CD can make it totally unusable.
Here are just a few examples of PS2 games:
Games for the PlayStation 2 are coming out at a rapid pace. Since it will play older PlayStation games as well, it offers an incredibly large existing game library. Game prices range from about $20 to $70.
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Special thanks to the staff at BuyRite Video for their assistance with the articles in this series.