I have a Hercules GameTheater XP, which claims to have hardware MP3 decoding, which seems stupid for a card targeted at P3+ systems.

http://www.dansdata.com/gtxp.htm

I dont think a hardware ISA MP3 Decoder exists as such however something close to it are the Mpeg decoder cards but im not sure they support any sound formats directly, only through mpeg video files.

I have another card which I haven't tested yet which is a Digigram PCX-20 broadcast card used in radio stations.
"PCX and LCM cards perform real-time, simultaneous MPEG Layer I and Layer II compression and decompression during record and playback. Support provided for Layers I and II of the MPEG Audio standard (ISO 11172-3) and the low sampling frequencies of the MPEG-2 Audio standard (ISO 13818-3)."

http://www.digigram.com/products/product_info … 9250&mode=specs

It basically states it will playback .mp2 audio files not sure if you need to use propreitry software or not, I think this card is the closest thing you will get to hardware decoding for audio and lets face it .mp2 sounds pretty good anyway,.

I have a Turtle Beach Santa Cruz which claims to offload mp3 playback but I haven't been able to test it. I want to compare playback with a Create Labs Ensoniq board to see if there is any CPU load difference.

Product Overview

The Santa Cruz represents the ultimate in DSP-accelerated, multiple channel
audio hardware for the PC featuring:

* Cirrus Logic SoundFusion(R) DSP architecture offloads MP3 playback
and other audio tasks from your PC's processor.

A question is which playback software will interface with these DSPs.

And I also wonder if they might be playing the advertising game and just marketing with MP3 buzzwords and don't actually specifically do MP3 decode at all. They could just be talking about hardware DirectSound mixing and pretending that makes a tangible speed boost to music playback.

CS46XX based cards like Santa Cruz have a DirectShow filter (CWCMP3.AX) in their drivers for MP3 decoding. I have been able to use it with Media Player Classic. But don't get too excited about it - it's buggy (garbled sound and dropouts every few minutes).
No idea about those Maestro/Canyon3D-based cards.

Thanks for the mention of these other cards. They all appear easier to obtain than the MX400. Sounds like I have a new experiment. 😀