http://web.archive.org/web/19970128235235/http://www.ensoniq.com/
http://web.archive.org/web/19970607101055/www.ensoniq.com/html/download.htm
http://web.archive.org/web/19970607100941/www.ensoniq.com/html/semiconductors.
htm     (-ref the IIGS here)

and if you need their old drivers :

http://web.archive.org/web/19970607101326/www.ensoniq.com/html/multimedia_prod
ucts.htm

-Bart