as electrical isolation for the circuit sub board 46 so that the circuit sub board 46 can actually attach to the main board 52 the second ground connection layer is closer to the main board 52 than the second power source layer however even if the second power source layer 48 of the circuit sub board 46 is closer to the main board 52 power source stabilizing and ground connection strengthening effects are still present although not as good as when the second ground connection layer 50 is closer to the main board 52 according to the embodiment of this invention the structure formed by attaching the aforementioned circuit sub board 46 to the main board 52 is achieved by piercing a plurality of guiding legs through the first power source holes 10 12 14 16 18 and the second power source holes 20 22 24 26 28 as well as piercing through the first ground connection holes 30 32 34 36 and the second ground connection holes 38 40 42 44 these guiding legs not only serve as a medium of connection and piercing but also serve as a tool for securing the circuit sub board 46 the computer system further includes a chipset 70 and memory module slots 58 60 62 64 66 and 68 the circuit sub board 46 has such a shape that most of the signaling lines between the chipset 70 and the memory module slots 58 60 62 64 66 and 68 are covered as shown by labels 54 and 56 in the fig4 and 5 because the fourth signaling layer is electrically connected with and close to the circuit sub board 46 this is equivalent to increasing the.