A cabinet having a plurality of compartments adapted to have disposed in a corresponding one thereof one of a plurality of processing unit modules. Each one of the modules includes a case. The case has a motherboard mounting surface adapted to have mounted thereto one of a plurality of differently configured motherboards, each one of the differently configured motherboards having a different arrangement of a CPU, main memory and I/O adapted cards. The case also has a bulkhead mounting surface adapted to have mounted thereto one of a plurality of differently configured I/O bulkheads, each one of the differently configured bulkheads being configured for a corresponding one of the differently configured motherboards. The case has a fan mounting surface adapted to have mounted thereto one of a plurality of differently configured fan assemblies, each one of the differently configured fan assemblies being configured for a corresponding one of the differently configured motherboards. The case is provided having a motherboard mounting surface adapted to have mounted thereto a CPU, main memory and an I/O adapter card. The I/O adapter card has a front lower edge adapted for plugging into the motherboard. A cover is adapted for mounting to the case over the motherboard. The cover has an anti-vibration member adapted to engage a rear upper edge of the I/O adapter card and maintain the I/O adapter card securely plugged into the motherboard when the cover is mounted to the case.