Abstract: Processor modules (2) are supported side-by-side with one another to slide in and out of a cabinet (1) on tracks (6, 7), each module (2) including a PC-CPU motherboard (11) and a hard-disk unit (16) mounted on a metal plate (3). Power is supplied to all the modules (2) in parallel from two power-supply units (18) mounted in the back of the cabinet (1), each comprising a pair of power-supply modules (19). The pairs of power-supply modules (19) supply power in parallel with one another to the processor modules (2). Diode circuitry (20) is included in each power-supply module (19) to isolate that power-supply module (19) from its paired power-supply module (19) in the event that a fault occurs by which the output voltage of the respective power-supply module (19) fall below that of the power-supply module (19) with which it is paired.