Abstract: A multiprocessor system is disclosed, which comprises a plurality of processor unit, such as eight processor units, and a plurality of interconnection bus that may be a dual unidirectional point-to-point bus. Every interconnection bus connects predetermined two of the processor units. Particularly, at least two of the interconnection buses are crossed to each other.

Abstract: A multiprocessor system according to this invention comprises a main board, an expansion board, and at least a connection card. The main board comprises a plurality of first processors, such as four (4) CPUs, and at least a first socket. The expansion board comprises a plurality of second processors, such as four (4) CPUs, and at least a second socket. The plurality of first processors selectively communicates with each other by way of a plurality of first processor buses, which may be dual unidirectional point-to-point buses such as HT buses. The plurality of second processors selectively communicates with each other by way of a plurality of second processor buses, which may be dual unidirectional point-to-point buses such as HT bus. The connection card(s) electronically connect(s) to the first socket(s) and the second socket(s) for providing connection between at least one of the first processor of the main board and at least one of the second processor of the expansion board.