You're on the five-yard line, and you've got your sights set on a rookie wide receiver who's wide open. The rain is coming down hard, but it's always raining in East Rutherford. As you raise your arm to throw, you see Paul Grasmanis in the corner of your eye. But before you can even blink, you feel your controller shaking violently in your hands. You've been sacked. Gaming has come a long way since the days of Pac-Man and Pong. The latest software is so realistic that players can almost feel the weight of a defensive tackle crashing down on them. But without the latest hardware, Madden NFL 2007 would be about as exciting as Solitaire.
The days of a single processor driving a game are long gone. The latest hardware accelerators let game designers forego canned explosions, gross approximations in lighting, and nonplayer characters with simplistic intelligence, delivering instead movie-quality images and lifelike environments where shadows, projectiles, and animals react as they would in the real world.
Today, hardware acceleration means addressing basics like audio, video, and computation. But even the computation is being augmented by Ageia's new PhysX processor. It offloads the computations necessary to simulate the physical gaming environment—tracking everything from a collision between a bullet and a jar to how many pieces the jar breaks into. This level of complexity allows games like Airtight Games' forthcoming Hangar Of Doom to have hundreds of moving objects on screen (Fig. 1).
THE MANY PLATFORMS
When it comes to the platform, the gaming industry remains split between consoles, PCs, and handheld devices. The handheld market is led by Sony's PSP and Nintendo's DS and Game Boy. But an increasing number of cell phones offers games, too (see "In The Palm Of Your Hand" at www.electronicdesign.com, Drill Deeper 12538).
Each of these platforms has its tradeoffs, so the level of hardware acceleration varies significantly. A PC can afford to have sophisticated cooling systems attached to the various hardware accelerators, but handheld devices must be power misers. Likewise, handhelds have a smaller screen that places its own constraints on the type and quality of games that can be developed.
Consoles seemingly hold an edge in gaming performance when they first appear. But PCs quickly jump to the front of the pack, due in large part to their quick-change video adapters. Of course, few PCs come equipped with high-end gaming-system capability, while consoles provide a consistent platform for game developers. This also makes consoles more powerful game platforms than the average PC.
COMPONENTS
Computer gaming used to be CPU-centric (central processing unit). Now you'll find two or more cooperating processor complexes. In the future, the CPU may hand tasks like artificial intelligence or search algorithms off to other hardware accelerators (see "Smart Gaming" online at Drill Deeper 12539). The CPU in a typical gaming system already passes off work to a number of different accelerators.
The most visible part of the gaming setup is the graphics processing unit (GPU). Other components include the physics processing unit (PPU)—a technology in its infancy (e.g., Ageia's PhysX processor)—and the audio processing unit. All told, these devices make today's gaming a far cry from an 8080 banging away at a bit-map screen for a line-drawn, Asteroids-style game.
Multicore, multiple-instruction/multiple-data (MIMD), and single-instruction/multiple-data (SIMD) architectures add further to the complexity for game developers, on top of the task of spreading gaming computation among a number of processing units. Fortunately, many processing units provide a simpler, black-box level of control that hides the growing complexity of the underlying hardware.
CONSOLES
Consoles represent the state of the art in consumer gaming, and it seems that IBM's PowerPC is the CPU platform of choice. Well, almost.
Microsoft's Xbox 360 has a CPU with three PowerPC cores (Fig. 2). Similarly, Sony's PlayStation 3 uses a version of IBM's Cell processor (see "Cell Processor Gets Ready To Entertain The Masses" at www.electronicdesign.com, ED Online 9748) (Fig. 3). It consists of a PowerPC core and a group of synergistic processor elements (SPEs) (Fig. 4).
The PowerPC's vector processing unit is one reason it's popular in gaming platforms. The Xbox 360 and the PlayStation 3 are both designed so that the various components complement each other in speed, interface, and layout. The Xbox 360 GPU/CPU connections, for example, are a block of parallel traces from one chip to the other. Differential pairs are the norm, given the high-speed nature of the connections.
The Xbox 360 consists of three major components. The CPU uses a conventional, multicore architecture with a shared level 2 cache. The PowerPC cores are identical. The Xbox 360 also features a unified memory architecture, which is one reason why the GPU doubles as the memory controller. The GPU's level 2 cache is fed from the data moving through the GPU from the off-chip memory.
The unified architecture makes lots of sense for gaming platforms. The CPU-based applications simply adjust the state of the virtual gaming world, and the GPU can immediately access it. The GPU does have its own rendering memory, which generates each frame so that the graphics core won't have to dominate access to main memory when it creates a display frame.