It consisted of up to three customized DSP boards that could be plugged into the expansion bus on a NeXT Computer (a "cube"). The ISPW could then run a customized real-time audio processing server on the hardware boards controlled by a client application on the NeXT.
Each ISPW card had two Intel I860 microprocessors (running at 80 MFLOPS). An additional card with eight channels of audio I/O was also available for multi-channel sound recording and playback. A three-board ISPW provided what was at the time unsurpassed signal processing and audio synthesis power on a single workstation. A single ISPW card cost approximately $12,000US (not including the computer), which made it prohibitively expensive outside of research institutes and universities.
And the I860 board :
The main server software developed by IRCAM for the ISPW was called FTS ("Faster Than Sound"). The main NeXT client application was a graphical program called Max, developed by Miller Puckette. A commercial version of Max (without the FTS server) was licensed by IRCAM to Opcode Systems (and, later, Cycling'74).
See also Pd.