While digging into the implementation of Sound Blaster compatibility on PCI cards, I found an unexpected gem. Ensoniq’s U.S. Patent 5,790,837 includes partial source code for the Sound Blaster emulation driver used with the Ensoniq Soundscape VIVO boards, SSINIT.COM.
The VIVO boards were Ensoniq’s last ISA-based product (introduced in 1995) and shared a common trait with the PCI-based ES1370 and later devices: There was no hardware Sound Blaster compatibility. Instead, Sound Blaster digital audio as well as AdLib FM synthesis were emulated.
Now the VIVO was a bit of a mixed bag. While the Sound Blaster compatibility wasn’t bad, it required EMM386 and a TSR and was therefore fundamentally incompatible with certain games. The AdLib emulation was not so much emulation as approximation, as it tried to replace a FM synth with wavetable synthesis, with mixed results. On the upside, the wavetable synth (1MB ROM) was not at all bad, and the cards were cheap (and therefore used in many OEM systems). Continue reading