My Pentium 166 MMX running Windows 95 and Winamp 0.x got 100% loaded while playing my first ever mp3 file - brought home on 3 floppy disks. That's why games of that era were using CD Audio for soundtrack or tracker music like Unreal or Deus Ex.
My old 233 MHz MMX Pentium machine could decode MPEG-4 standard definition video with an MP3 audio track, under Linux. Though I had to set my video player to real-time priority if I wanted it to not drop frames.