AMD InterWave
The great potential of the original UltraSound enabled Advanced Gravis to license the new GFA1 chip and software to AMD, who were trying to make it into the sound chip market at the time. The chip, released in 1995, was named AMaDeus, with the AMD part number of Am78C201 and was marketed as InterWave. It was enhanced to handle up to 16 MB of onboard memory, IMA ADPCM-compressed samples, have no sample rate drop at full 32 voices, and featured additional logic to support hardware emulation of FM synthesis and simple delay-based digital sound effects such as reverb and chorus. It was compatible with CS4231 codec installed in the UltraSound MAX or 16-bit recording daughterboard for the UltraSound Classic.
The sound "patch set" was reworked from a collection of individual instrument .PAT files to a unified .FFF/.DAT sound bank format, resembling SoundFont, which could be either ROM or RAM based. There were 4 versions of the sound bank: a full 16-bit 4 MB with 8-bit downsampled 2 MB version, and 16-bit 2 MB (different sample looping) with 8-bit downsampled 1 MB version. A converter utility, GIPC, was provided for making .FFF/.DAT banks out of .PAT/.INI collections.
The reference card contained 1 MB μ-law ADPCM compressed sound ROM, which contained basic General MIDI voices and sound samples to help FM emulation, and 2 slots for RAM expansion through 30-pin SIMMs. The IWSBOS emulator was reworked to include Mega-Em features such as General MIDI emulation, and the SBOS kernel was included in Windows 95 drivers to provide emulation in a DOS Box window.
The process of patching middleware sound 'drivers' was greatly simplified with PREPGAME utility, which could fix most known DOS games automatically either by correctly installing and configuring native InterWave drivers or replacing the binaries for some rare devices like Covox. It could also update DOS/4GW extender to work around its 16-bit DMA bug.
The GFA1 featured a GUS/MAX compatibility mode, but base card was not compatible with UltraSound Classic unless some memory was installed.
The InterWave technology was used in Gravis UltraSound PnP line of cards. It was also licensed to various OEMs such as STB Systems, Reveal, Compaq, Dynasonic and ExpertColor. Some high-end OEM variants contained full-blown 4 MB patch set in ROM and proprietary hardware DSPs to enable features like additional sound effect algorithms and graphic equalizer.
Software drivers for the InterWave were written by eTek Labs, containing the same development team as the earlier Forte Technologies effort. eTek Labs was split off from Forte Technologies just prior to this effort. In August 1999, eTek Labs was acquired by Belkin and is currently their research and development team.
Read more about this topic: Gravis Ultrasound