What has happened to EAX and other hardware sound enhancements? [closed]

Perhaps you should look at Jeff Atwood's blog on sound cards from May 4th, 2011.

The default, built-in sound chips on most motherboards have evolved from "totally crap" to "surprisingly decent" in the last 5 years. But besides that, in this era of ubiquitous quad core CPUs nearing 4 GHz, it'd be difficult to make a plausible case that you need a discrete set of silicon to handle sound processing, even for the very fanciest of 3D sound algorithms and HRTFs.

If Jeff is considered to be an expert, the need for EAX support died when processing power became sufficent to no longer require external hardware.

From the Wikipedia artcile on EAX:

According to Creative's OpenAL 1.1 specification, EAX should be considered deprecated as a developer interface. New development should use OpenAL's EFX interface, which covers all the EAX functionality and is more tightly coupled with the overall OpenAL framework

From Creative's post explaining OpenAL and Windows Vista (and subsequently Windows 7):

With Microsoft's decision to remove the audio hardware layer in Windows Vista, legacy DirectSound 3D games will no longer use hardware 3D algorithms for audio spatialization. Instead they will have to rely upon the new Microsoft software mixer that is built into Windows Vista. This new software mixer will give the users basic audio support for their old Direct Sound games but since it has no hardware layer, all EAX® effects will be lost, and no individual per-voice processing can be performed using dedicated hardware processing.

Legacy EAX games will likely not perform correctly on Windows Vista and Windows 7. From this March 09, 2011 of the Auzentech X-Meridian 7.1 2G Sound Card:

We cannot fault any current sound card for lacking the ability to enable EAX in legacy games. EAX is no longer a standard used in PC game audio. If it works in a game, it is simply a bonus to the sound card buyer.

When EAX came out it was necessary for games to enable EAX for the game to utilize the hardware. Since DirectSound is no longer supported game developers should be using OpenAL, which enables hardware acceleration automatically (if supported by the device) or is otherwise handled through the software.

The list of OpenAL supported games is not extensive (in my opinion) but not all games require a highly emersive sound experience.

I concur with Jeff. Game audio processing is just math, whether it's plain old mixing or the fanciest of DSP or EAX effects. Given the virtual explosion in CPU power, it's difficult to see the advantages of having a dedicated DSP for audio. Software is not only powerful, but it also lets you choose from a huge variety of very cool audio effects, either that a game developer could write themselves, or license from the same companies that make professional audio plug-ins.

That said, it is very worthwhile to make sure your system has a good quality converter; that's often the best reason to update your sound card (particularly for laptops, which can be notoriously noisy systems).

So most games these days use software-based audio engines; the sophisticated games use APIs, which are paired with GUIs for the sound designer, such as FMOD, Wwise, XACT.