I'm not certain they would be completely computerless if they are still producing these days (haven't seen any news) but Warp Records stuff of that era was heavily based on live and studio electronic instruments for sure. Its been a big influence for leftfield artists over the years. BOC certainly managed to poke their heads above the surface influencing the likes of Daft Punk and Moby, Radiohead etc. Not to mention the much adored Aphex Twin also of Warp lineage ...
RE: Grapthar's Daily Hive Music Feature: Boards of Canada - 'Telephasic Workshop'