I'm a huge fan of backwards compatibility. Frankly, I think everyone should be, what's not cool about being able to play your old games on a new system? Better yet if you've never owned the old system you suddenly have a sizable library of game accessible to you with new ones to look forward to. It's quite possibly one the best features for a game console to have. But it's not always done right, either because it's too expensive to implement all the past features, or just too impractical. With that said, lets take a look at the console that did it, and how they did.
Atari 7800-backwards compatible with Atari 2600
So my first system was an Atari 7800. After crash of 83-84 Atari was no longer relevant in the market. Nintendo came in a revitalized the market with the NES, and Atari thought they could get back into the race with a new system, enter the 7800. They wanted to rectify the problems with the 5200 (the size of the console, wonky controller, no backwards compatibility) and in that sense they succeeded. The 7800 is fully backwards compatible with 2600 games (but not 5200 games), you could even use the same controller if you wanted. As far as I'm concerned it was a great call and worked really well. To this day people track down the 7800's for that reason.
Sega Genesis-backwards compatible with Sega Master System
A lot of people don't know about this one, but the hardware for the SMS was built into the Genesis. You did however, need a converter to accept the cartridges. It's called the power base converter and it goes right over the top of the system to accept both types of SMS games. The problem is you have to take it off to play your Genesis games again. Say what you want about the monstrosity that was the 32X was, at least you didn't have to disconnect it to play Genesis games. That and the lukewarm reception of the SMS (at least here in the US) is probably the reason it's an obscure piece of hardware. They cost more than the SMS itself now, so there's little reason to own it.
Playstation 2 backwards compatible with Playstation 1
This is really the grand daddy of backwards compatibility. See, back in 2000 it just wasn't normal for a game system to be nativley backwards compatible with their successor, better yet compatibility a system that was already massively popular with no extra steps, and having DVD capabilities too! It's little wonder that the PS2 flew off store shelves in 2000. It was the reason I bought one on launch day even though there weren't any games that I really wanted. The controller ports were the same so all the accessories were compatible too, but the Dual Shock 2 did everything the Dual Shock 1 did (and more) so there was little reason to even keep the original controller. The memory card ports were also the same, and while you sadly couldn't use PS2 memory cards for PS1 games you could transfer saves over to a PS2 card as an overflow. It was a really nice touch. And to top it all off you could use component video and a toslink connector for better audio/video fidelity. For its time, that was an impressive piece of technology for a very reasonable price. There is almost no reason to own a PS1 today, which is why they sit on Goodwill shelves for just a few bucks.
Game Boy Advance-backwards compatible with Game Boy/Game Boy Color
I could go into a lengthy discussion about the Game Boy Color, but I decided to condense this section as the GCB is fundamentally a half step: a stop gap system. With that said, the GBA came out in 2001 and could do everything the previous systems could do, and of course, play the new games coming out. Adding a splash of color to previous monochrome games was a nice touch as well. Rhe screen was improved and so were the speakers. The screen itself was wider on GBA so you could stretch it to get more real estate or keep the original aspect ratio. If you got the GBA SP you got a nice backlit screen, rechargeable battery and a clam-shell design to protect the unit. Not too shabby! Sure the GB and GBC cartridges protrude a bit, but it's hard to argue with all the other features. To this day, the GBA SP is the most desirable model of the Game Boy.
Nintendo DS- backwards compatible with Game Boy Advance
Okay so another thing a lot of gamers don't know is that the DS was never originally designed to be the successor to the GBA, it just kind of happened that way through osmosis. Nintendo has always had this vision for a "third pillar" as something that bridges the gap between handheld and console. The best example of this is the ill fated Virtual Boy. I actually wouldn't be surprised if this pops up again in the future.
Anyway, the DS's "backwards compatibility" with the GBA (but not GB or GBC) was more or less meant as a staple to an otherwise risky endeavor. Back in 2004 the DS was treading on new ground and Nintendo wanted something to solidify the system: to give it an immediate value proposition. In addition to this they also wanted to use that cartridge slot for other functionality (such as added RAM for the web browser, rumble pack and MP3 player). The compatibility itself is functional but Some of the accessories are incompatible and it can't link to the GCN. Its also limited GBA games to single player only and the DS is much bulkier with shorter battery life. A. Even if you went with the DS lite which fixes some of those issues it's still inferior to what the GBA could do. For what it's worth it's a nice feature to have in the original DS models as opposed to the DSi which omitted it entirely. But neither system has much of a demand compared to the 3DS.
Xbox 360-Backwards compatible with Original Xbox
The original Xbox was basically built like a traditional PC, if you ever open one up you can see all the universal PC components. But it was always sold at a loss, the cost of the components were exorbitant compared to it's direct competitors. The architecture is simultaneously the systems greatest strength and weakness. So Microsoft wisely decided to change the architecture to Power PC to save space and money. Well that left backwards compatibility on the table. Considering how soundly the PS2 leveled the competition (due in part to their backwards compatibility) Microsoft wanted every advantage they could. The only option other than including the original hardware was emulation.
The emulation is inconsistent to say the least. Approximately 50% are compatible, and for the most part it's a hit and miss sort of deal. Some games work others don't. The ones that do work, work relatively well, there are minor glitches, often widescreen doesn't work or CGI cut-scenes don't play properly, and you need an official hard drive to make that work (or add the emulation file to a third party drive), but it's better than nothing I suppose. At the end of the day though, if you want to play original Xbox games, get an original Xbox, they are really affordable.
Playstation 3-backwards compatible with Playstation 1 and Playstation 2
I know what Sony was going for in 2006, a machine that had no equal. That was the Achilles heel of the PS2 was that it couldn't match the audio/visual prowess of the Xbox and Gamecube. Hence the PS3 having all the features under the sun (including Linux and SACD Support) with a price $600 price tag to make it all possible. We all know the story, $600 was a lot of money to a lot of people, so some features got axed, including PS2 compatibility, thankfully PS1 compatibility was retained.
It was great while it lasted, you made virtual memory cards on the system eliminating the need to buy them (there was even an accessory to port saves over) games were also upscaled to HD via the HDMI cable, even online play was preserved. Sure a lot of the accessories lost compatibility but 3 generations being playable by 1 system is hard to argue with.
Today the original models still fetch a pretty penny but they tend to not be stable (Yellow light of death) they are large and have a small hard drive. Compared to the PS2 slim (which is a little larger than a DVD case, more reliable common and cheaper) it's hard to justify purchasing an original model PS3.
Wii-Backwards compatible with Gamecube
Similar to the experimental nature of the DS, Nintendo wanted to branch out with the Wii. Once again they took a similar approach by adding backwards compatibility. The ports were right on the side of the console, and support was native. Nearly every accessory was compatible, and the component cable issue was mercifully fixed, they even added GCN controller support for many Wii games. The only real losses were the GB player and the Broadband adapter.
Even as an avid Gamecube fan, I have a hard time justifying owning on in light of the Wii. I do dislike the ports being on the side and the inability to launch games using the GCN controller, but those are minor inconveniences compared to what is gained. What Nintendo should have done was make a standard wireless controller to function for both Wii and GCN, sadly this is not the case. Clunky, but well done, hence why GCN's share shelf space at the local Goodwill.
3DS-Backwards compatible with DS
In many ways the 3DS just feels like a natural evolution of the DS. Nearly everything is virtually identical. I even showed one of my friend's mom's my 3DS she asked what the difference was other than the circle pad. The game cards are nearly identical, and function exactly the same way. DSiware transfers seamlessly over, and the circle pad works in place of the d-pad making some games more comfortable, and online play worked as well while it was operational.
Being such a natural transition there's little reason to own a DS today. They hold their value a little better than PS1's and Gamecube's, but expect them to drop even more. 3DS's popularity is pretty close to what the DS's was in its heyday, and I expect the next generation to be more of a departure. Long story short, the 3DS will probably be the definitive handheld to own to play those games.
Wii U backwards compatible with Wii
Given the popularity of Wii, it was a no-brainer to include backwards compatibility on Wii U. It's compatible with all Wii games and outside of Gamcube controller support, it's fully functional including online play up until the servers were shut down. The Wii U could also upscale Wii games via HDMI, which is always a welcomed feature. Wii remotes can be used interchangeably but Gamecube support is omitted entirely.
The biggest gripe I have with the Wii's backwards compatibility is the fact that I have to boot a the old Wii menu in order to boot a Wii game. Similarly, Wiiware, and Wii virtual console games have to be accessed through this menu. It's nice that off screen play was added via the gamepad, but games can't be controlled with with it so it's a almost useless. I'd rather have it than not, but I wish it was better implemented. The Wii was always an affordable system, but they still have a bit of demand due to the Gamecube functionality. Much like the DS, I expect their price to drop even further.
Vita backwards compatible with PSP
Now this one is a bit of a stretch, and I debated whether I was going to include it or not, but Vita is technically backwards compatible, even if it is only partially. The reason I had the issue is that it's only compatible with PSP software, not hardware.
Much like the original Xbox the greatest strength of the platform was also the weakest: the UMD disc. While they could hold 1.8 GB of data, they were fragile (not a good attribute to have for a handheld game format) sluggish to load data, and drained the battery with moving parts in the drive. It was one of those things that sounded a lot better on paper, than worked in execution.
Sony made a compromise, put in the hardware to play the games, but omit the drive. While it sucks to be limited to digital downloads, it sucks more that they aren't all available online and are more expensive than their UMD counterparts. I don't blame Sony for their call the same way I don't blame MS for theirs on the Xbox 360. It was the most pro consumer choice they could have made. PSP's still hold more value than DS's and I'm betting that's the biggest reason.
So there you have it, sorry if it read more like an encyclopedia than a blog, but it's a subject that I've been meaning to tackle for a while now. On a side note I'd be interested to hear about how Playstation Now functions. While it's not backwards compatibility, it's an interesting way to offer similar functionality. If it's priced properly it could be a viable alternative.