Complex sentence: The machine suffered when applied to general purpose database application environments, not least becuase the I/O subsystem over-relied on the central processing power (much as the VAX did) and thus used relativly dumb I/O processors.
Split into simpler sentences: The machine suffered when applied to general purpose database application environments. Not least becuase the I/O subsystem over-relied on the central processing power (much as the VAX did) and thus used relativly dumb I/O processors.