Scalable system for high-performance computer, comprising • a plurality of motherboard chassis inserted in a computer rack mounting kit, • each motherboard chassis, called inner chassis, having front and rear longitudinal ends, being open at these ends, and being configured to receive at least one motherboard module comprising motherboard connectors, said motherboard module being inserted by a first longitudinal end of the inner chassis, • said plurality of inner chassis forming a stack of inner chassis, the stack being configured to receive an outer floating bracket chassis, said outer floating bracket chassis being inserted by a second longitudinal end of each inner chassis forming the stack of inner chassis, • said outer floating bracket chassis housing a cable box, configured for connecting to each other the motherboard connectors of a plurality of motherboard modules arranged in the stack of inner chassis, and at least one double floating bracket housing cable connectors of the cables of said cable box, • the system being characterized in that said double floating bracket comprises: i. first floating attachment means configured to guide the double floating bracket in the outer floating bracket chassis by aligning upward and downward said double floating bracket with an inner chassis, ii. second floating attachment means configured to align the cable connectors of the cables of said cable box with motherboard connectors of each of the motherboard modules. • a plurality of motherboard chassis inserted in a computer rack mounting kit, • each motherboard chassis, called inner chassis, having front and rear longitudinal ends, being open at these ends, and being configured to receive at least one motherboard module comprising motherboard connectors, said motherboard module being inserted by a first longitudinal end of the inner chassis, • said plurality of inner chassis forming a stack of inner chassis, the stack being configured to receive an outer floating bracket chassis, said outer floating bracket chassis being inserted by a second longitudinal end of each inner chassis forming the stack of inner chassis, • said outer floating bracket chassis housing a cable box, configured for connecting to each other the motherboard connectors of a plurality of motherboard modules arranged in the stack of inner chassis, and at least one double floating bracket housing cable connectors of the cables of said cable box, • the system being characterized in that said double floating bracket comprises: i. first floating attachment means configured to guide the double floating bracket in the outer floating bracket chassis by aligning upward and downward said double floating bracket with an inner chassis, ii. second floating attachment means configured to align the cable connectors of the cables of said cable box with motherboard connectors of each of the motherboard modules. i. first floating attachment means configured to guide the double floating bracket in the outer floating bracket chassis by aligning upward and downward said double floating bracket with an inner chassis, ii. second floating attachment means configured to align the cable connectors of the cables of said cable box with motherboard connectors of each of the motherboard modules.