The SiS656 features a PCI Express x16 Bridge and Dual-Channel DDR2-667 / DDR400 Memory controller, supporting Pentium® D Dual-Core processor and Pentium® 4 FSB up to 800MHz. The SiS656, via the second-generation 1GB/s Multi-threaded I/O link, interconnects with the SiS965 Media I/O that integrates two PCI Express x1 ports, one EHCI compliant USB 2.0 host controller, 3 OHCI compliant USB 1.1 host controllers, a SATA 150 controller, an ATA 133 dual IDE controller, an AC'97 v2.3 compliant audio controller, and a Gigabit MAC controller with standard GMII/RGMII interfaces.

The SiS656 Host Interface features AGTL & AGTL+ compliant bus driver technology with integrated on-die termination to support Intel® Pentium® 4 series processors with Hyper-Threading Technology and bandwidth up to 6.4GB/s. The SiS656 PCI Express x16 Bridge, compliant with PCI Express SPEC 1.0a, provides bandwidth up to 4.0GB/s.

The SiS656 Dual-Channel Memory Controller, delivers bandwidth 10.6GB/s (DDR2-667) or 6.4GB/s (DDR400), more than sufficient for 800MHz Pentium® 4's FSB bandwidth demand of 6.4GB/s complement. There is still lots of bandwidth to spare for the multi-I/O masters and PCI Express x16 Bridge.

The SiS656 Dual-Channel Memory Controller supports 3 flexible operating modes, (1) Legacy 64-bit mode for Single-Channel memory support, (2) Single 128-bit mode for Dual-Channel memory support with identical size and type RAM (3) Concurrent dual 64-bit mode for Dual-Channel memory support with different size and type RAM.

The SiS656 incorporates the second-generation 1 GB/s MuTIOL® interface to bridge the SiS965 Media I/O. SiS MuTIOL® technology is developed in three layers, namely the MuTIOL® transaction layer, MuTIOL® link layer, and the MuTIOL® physical layer. Based on the SiS656 with optimized ball-out, a Pentium® 4 system featuring the Dual-Channel DDR2-667 / DDR400 memory and a PCI Express x16 graphic slot can be realized in a cost-effective 4-layer PCB.