Ferrocores used in earlier VX models. Nowadays, these ferrocores use photoquaternial quantum effects, so they can be made much smaller.

The ferrocore is responsible for channeling threads (sometimes referred to as paths) and stabilizing flux in a VX unit.

Due to the corrosive nature of the hypervolt interference run through it (often around 2-9 MTr), the ferrocore wears out quickly and is one of the first modules tested during system diagnostic tests. The first replacement of the ferrocores on a rig is seen by many VX enthusiasts as a rite of passage into expert-level experimentation.

Though the Synclex Corporation claims that its chromium cores, introduced in 2010, circumvent the problem, comprehensive field testing has yet to confirm this claim.

The ferrocores are controlled by the central control unit via PROFIBUS (whose contacts resemble somewhat widened serial connectors) in all models after 1992, whereas earlier models usually use three-prong HH cables as defined by UTF-5. However, it is not unusual to see early models with peer-to-peer trielectric cables.