The ultimate computer, computronium has been described as "programmable matter".  In fact it is a remarkable feat of nanotechnology, the shrinking of a computer to the atomic scale.  Before Era-3, even the best nanoforges in the galaxy couldn't produce a sample of computronium above 5% in purity. 

It is said that the core of Troniac, the Computer-God was made of pure computronium. After the Battle of the Pillars, during the 1000 Years War, when Troniac its self took some substantial damage, fragments of purportedly pure computronium started circulating among Troniac Cultists that were supposed to be fragments of Troniac's core.  These shards were often kept as holy relics, and many of these formed the basis of the known Avatars of Troniac, and some of the more dubious samples formed the minds of some of the Mad Saints of Troniac.

There were also a few sources of naturally occurring computronium.  This was exceedingly rare, as the natural processes necessary to deposit the right minerals in the right configuration proved extremely complex.  Yet, given enough time, space, and matter, nature found a way.  These natural computronium deposits only ever produced a material of very low purity, generally regarded as junk by anyone on search of computer power, yet endlessly fascinating to anyone interested in geology or computer science.

Computronium above a certain critical mass, tends to be independently sentient.  Unless the computronium is formed in a certain way, so as to properly integrate it into an interactive environment with a suitable suite of inputs and outputs, it tends to be hopelessly insane.  As a result of these facts, the Planetary League heavily regulated the production of computronium within its borders.  In spite of these same facts, Gazillion, inc continued to produce computronium in many of its own facilities, often enslaving the resulting AIs to power its technological empire.