The SiS649 features a PCI Express x16 Bridge and flexible Single-Channel DDR2-533/DDR400 Memory controller, supporting Pentium® D Dual-Core processor and Pentium® 4 FSB up to 800MHz. The SiS649, 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, a 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 SiS649 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 6.4GB/s. The SiS649 PCI Express x16 Bridge, compliant with PCI Express SPEC 1.0a, provides bandwidth up to 4.0GB/s.

The SiS649 Flexible Single-Channel Memory Controller, delivers bandwidth 4.2GB/s (DDR2-533) or 3.2GB/s (DDR400).

The SiS649 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.