This paper describes newly developed advanced ATM switching system hardware structures based on MCM-D micro-processor modules. The Si-Substrate MCM-D technology which integrates micro-processor, interface control and peripheral control custom VLSIs, high-speed S-RAMS, and FPGAs (Field Programmable Gate Arrays) is employed. An MCM-D micro-processor module is realized by combining a Motorola 68030, high-performance ASICs, and high-speed S-RAM caches. This is made possible by high density packaging and high-speed 4M-byte with parity cache using 25 ns access to 4-Mbit of S-RAM memory. The MCM employs 12 S-RAMS, possible with the stacked RAM technique, to reduce the module size by 718 compared to conventional surface mounting modules. This micro-processor module technology and MCM technology will advance the development of practical B-ISDN ATM switching systems.