Not much has changed in the chipset architecture of the Sis756, compared to its predecessor, the SiS755/755FX for AGP. The SiS756 is of course new and uses PCI Express, so it features an x16 PCIe slot instead of AGP 8X. The Southbridge connection is still established via the proprietary SiS protocol called MuTIOL, providing up to 1 GB/s bandwidth.
If you thought SiS was going to connect the chipset components via PCI Express, you're going to be disappointed. The new Southbridge SiS965, though itself a new product, is intended to be used with other Northbridges as well, including ones not using PCIe.
The 965 now offers four Serial ATA connections. These are still compliant with the SATA I standard, offering 150 MB/s of transfer performance, and providing no support for command queuing as yet. That is due to come during the second half of the year, by way of an AHCI-compliant controller in the SiS966.
Nothing can yet touch NVIDIA's Active Armor firewall, so SiS responded with a simpler and cheaper upgrade: the network controller of the 965 can now also do 1 Gb/s. Two x1 PCI Express connections are provided to this end, which in practice should be enough for a while.
SiS will not have a new Southbridge supporting SATA II out until mid-year.