The SiS656FX features a PCI Express x16 Bridge and flexible Dual-Channel DDR2-667/DDR400 Memory controller, supporting Pentium® D and Pentium® 4 FSB up to 1066MHz. The SiS656FX, via the second-generation 1GB/s Multi-threaded I/O link, interconnects with the SiS966 Media I/O that integrates two PCI Express x1 ports, a EHCI compliant USB 2.0 host controller, 2 OHCI compliant USB 1.1 host controllers, a SATA controller compliant with AHCI 1.0, an ATA-133 dual IDE controller, an Audio controller with either AC'97 v2.3 interface or High-Definition-Audio v1.0 interface, and a Gigabit MAC controller with standard RGMII interface.

The SiS656FX Host Interface features AGTL & AGTL+ compliant bus driver technology with integrated on-die termination to support Intel® Pentium® D and Pentium® 4 series processors with Hyper-Threading Technology and bandwidth up to 8.5GB/s. The SiS656FX PCI Express x16 Bridge, compliant with PCI Express SPEC 1.0a, provides bandwidth up to 4.0GB/s.

The SiS656FX Flexible Dual-Channel Memory Controller, delivers bandwidth 10.8GB/s (DDR2-667) or 6.4GB/s (DDR400), 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 SiS656FX incorporates the second-generation 1GB/s MuTIOL® interface to bridge the SiS966 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 SiS656FX 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.