With the next generation of consoles just on the horizon, the Microsoft and Sony and Nintendo fans have already begun speculating on the specifications for each new system. And while those kinds of discussions of millions of polygons can be interesting at some level, the true geek in me finds it more engaging to consider whether any of this coming generation of console hardware will have any backward compatibility with the current generation or even previous generations.

What are the potential benefits of backward compatibility? How has backward compatibility worked out in previous generations of console hardware? And, given these things, what could Microsoft and Sony and Nintendo be planning for their upcoming consoles?

Sony's Hardware Solution

Certainly, one of the reasons that I was plenty eager to stick with the PlayStation 2 over the GameCube and Xbox was that I could keep playing my two dozen PSOne games on the new system. In fact after having my PS2 for a few months the bottom seemed to fall out of the PSOne used game market, and I found my library of older games growing rapidly. Granted, they weren't all great games, but when the price is so low, I can lower my standards. (I do still regret buying Loaded, though. Take this as fair warning, and stay far, far away.) It is regrettable that I own two of the handful of PSOne games that don't work well on the PS2, but given how well all my other games work, given that the PS2 can modestly enhance the graphics of most PSOne games, and given how many PSOne save games I can store on a single PS2 memory card, I happily made the switch. Since the PlayStation 3 will feature backward compatibility with both the PS2 and the PSOne, it readily provides an upgrade path for me and tens of millions of other PlayStation owners.

The reason that the PS2 can play PSOne games, however, is that the input processor on the PS2 is the same as the main processor on the PSOne. This is apparently a bit of a technical fluke, and so it is unclear how Sony intends to achieve backward compatibility on the PS3. The reports of exactly what will go into the PS3 are still of in flux, but if Sony includes enough PS2 hardware in the PS3, then it is possible they will achieve the goal this time by a similar means. Regardless, if Sony makes full backward compatibility work then they will have the first console that will play three generations of video game software.

One interesting question is that of why Sony wishes to continue supporting the games on its older systems. If they derive an important revenue stream from this practice, it's not altogether obvious; many people don't know about the PSOne compatibility of the PS2 and it is probable that only a fraction of those who do know actually consider it an important feature. Further, one could argue that providing support for your older platform dilutes the sale of next generation games, since the older games will necessarily be available more cheaply even if they are less graphically appealing. The lesson of the Commodore 128 seems appropriate here: even after the new C128 was released, it was the Commodore 64 game market which continued to thrive, leading most C128 owners (like myself) to run their machines in C64 mode almost all the time. Since this only grew the market of people who could play C64 games, the market for C128-specific games was stillborn. This isn't going to happen to Sony, obviously, since they will be providing must-have software for their new platform, but it does point out how an older platform could erode sales for a newer one when backward compatibility is part of the equation.

Still, with backward compatibility on their side, Sony may be the only company who enters the next generation confident that early adopters will have a huge library of older games to choose from while they endure the slow months after a hardware launch.

Nintendo: The Great Recycler

In this sense, I think Sony has taken a page from Nintendo's GameBoy strategy: get the players into your system, and keep them there from one generation to the next by ensuring that older games work with newer systems. Every new GameBoy model has stood on the shoulders of its predecessors, sharing much of the same hardware, and tempting players like me to buy a GameBoy Advance even though we already own a previous incarnation. (I already own a GameBoy Color, and I don't plan on giving it up, primarily for sentimental reasons.) Additionally, my growing library of games includes newer GameBoy Advance games as well as a smattering of GameBoy Color and GameBoy games, all of which I hope to carry with me when Nintendo announces a true successor to the Advance system.

Interestingly, Nintendo has rarely used any form of backward compatibility in their console hardware. The Super Nintendo Entertainment System (SNES) was not backward compatible with the giant library of Nintendo Entertainment System (NES) games already on the market. The Nintendo 64 (N64) was similarly not backward compatible, although a third party add-on provides a way to play NES and SNES games. As Nintendo's first optical disc-based system sold in North America, the GameCube was necessarily not able to play games from any of the previous cartridge-based systems. Unlike Sony, Nintendo has been willing to treat each new platform as a fresh start, relying on the previous generation only for the development of various franchises, like Mario and Pokémon. (It is perhaps a notable distinction that Sony's second console, the PS2, has not necessarily sold stongly because of their stable of franchises but rather on the strength of a newly revived franchise, namely Grand Theft Auto III and Grand Theft Auto: Vice City.)

Nintendo has started to realize the value of backward compatibility, I believe, but in a way that appears more lucrative than Sony's strategy. There are three aspects of Nintendo's current generation of hardware that exhibit this:

• NES and SNES Ports: With games like The Legend of Zelda: A Link to the Past, the Super Mario Bros. series, and Metroid: Zero Mission appearing on the GameBoy Advance with regularity, it appears that Nintendo realizes that many of their older, beloved games are ripe for reselling on their portable platform. Then there are the NES games that can be played via the e-Reader, a hardware dongle that reads games via swiped paper cards. The e-Reader approach makes money in two ways: first by selling the e-Reader hardware, and then by selling game cards themselves.
• The GameBoy Player: This isn't backward compatibility, necessarily, but something I'd call cross-compatibility, and it also isn't the first time Nintendo has dabbled in this direction. With the GameBoy Player, the GameCube has access to the huge library of GameBoy, GameBoy Color, and GameBoy Advance games on the market, all playable on your larger, brighter TV screen. Again, they can make money through hardware sales for the Player itself, and then later on new games. Furthermore, it weds a buyer even more strongly to Nintendo's line of products. (As I said, this isn't the first time Nintendo has had such a product: the Super GameBoy for the SNES allowed you to play GameBoy games on your TV. In the sense that it had Super GameBoy enhanced games, and exclusive special versions like Space Invaders which were nearly arcade quality, it shared some characteristics of being its own platform, like the e-Reader.)
• NES/SNES/N64 Emulators: With the release of The Legend of Zelda: The Wind Waker, Nintendo included a Nintendo 64 emulator that plays Ocarina of Time, the Zelda game from the previous console generation. A later version includes emulations of the two Zelda games released for the NES as well as Ocarina and Majora's Mask for the N64. Metroid Prime also has an unlockable emulated version of Metroid for the NES. These bonus items are intended to move games and thereby strengthen the GameCube platform.

The idea of the e-Reader is a neat trick, really. Think about it: Nintendo sells you hardware (GBA) on top of which you purchase yet another piece of hardware (e-Reader) just so you can buy games in all new format (cards). We've seen this kind of approach before but then it was Sega, not Nintendo, and they were trying to sell the SegaCD and the 32X on top of the Genesis. Those were both failures, for various reasons, and Sega lost some credibility over them. On the other hand, it appears that Nintendo knows how to take the idea, modify it, and make it work. They're the only ones making games for the e-Reader and they're not trying to build a new platform out of it, like Sega was trying to do. Rather, they're just efficiently making money using existing material from an older system.

Which is all to say, Nintendo has mostly responded to backward compatibility for its consoles in a unique way: software emulation and porting. I believe that one benefit that isn't apparent now is that with the tools they've built this generation they will be able to build emulators easily on their next generation of hardware and then resell the same software all over again in a new form. That is, they could port their current NES, SNES, and N64 emulators to the GameCube's successor and be ready to pack in their older Zelda games with a new Zelda game on the new platform. If they're lucky, they might even have a GameCube emulator to allow them to include Wind Waker as well. Certainly, Nintendo might have been slow to realize the value of backward compatibility, but they've ultimately created a way to add real value for their bottom line. Regardless, it does leave open the question of how Nintendo can induce its current customers to stay loyal when the GameCube's successor is launched. It seems unlikely, given their record, that Nintendo will offer a system that plays GameCube games out-of-the-box.

Microsoft the Unknown

Which brings me to the last player in this game: Microsoft. After a shaky start for the Xbox, they've stabilized into a respected second or third to Sony's dominating first. Going into the next generation, they've got a modestly strong base of Xbox owners, but they need to get those owners to upgrade while also bringing along some new customers at the same time. It is possible that backward compatibility with the Xbox in the next generation Microsoft console hardware would ease the transition for existing customers, while providing a strong library of older, budget-priced titles for new owners. However, what's currently believed about that future hardware may outright preclude any thought of backward compatibility with the original Xbox:

• The new machine is said to be based on one or more IBM PowerPC G5 processors as opposed to the single Intel Celeron in the current machine. Certainly the little-endian/big-endian issues can be overcome, as Mac coders have been doing for years, and the processor(s) may be fast enough to achieve playable speeds, but there are so many things that can go wrong that one wonders if the effort is worth the reward. One could say this is a big reason that Microsoft bought VirtualPC from Connectix a while back, but I really doubt that's the case.
• ATI is said to be providing the video hardware for the new machine, not NVIDIA who provided the hardware for the original Xbox. If there were any special features of NVIDIA hardware that were exploited by Xbox games, then those features may be either missing or accessed differently on ATI hardware. Consequently, any Xbox emulation would need to account for these differences at runtime.
• Current reports suggest that local storage may be in the form of removable media, like flash memory cards, instead the current Xbox hard drive. An Xbox emulation would require that the new local storage format remain compatible with the old hard drive storage.