Two Chipsets At The Same Time: SiS 656 And 756
A comparison of the two chipset diagrams shows that both use the same Southbridge components. This is by no means undesirable, since it enables designers to use the same components in multiple chipset configurations.
Intel offers three different ICH6 Southbridge chips for its 900 chipset series, VIA offers its VT8237 for K8T800/890 and its PT894 Pro. All these vendors use proprietary connectors, all of which are compatible only within their own core logic products.
ECS puts these circumstances to work and fits out its PF88 Extreme with the SiS656. This explains how the motherboard works with P4 processors up to the maximal FSB1066 specification, as well as with DDR2-533 memory. The chipset even anticipates higher clock rates in the future, although the BIOS of the PF88 Extreme currently doesn’t permit their selection (or overclocking). Again, revision 1.1 will change this and introduce popular overclocking options.
The choice of SiS chipsets is a happy coincidence because SiS is the only chip vendor to date to develop storage drivers (including RAID arrays) as well as AGP only - there is no chipset driver package for the Northbridge or PCI Express. Because the same Southbridge works with both CPUs, a SiS-based Windows installation is supposed to keep working, even when the user switches from a Pentium 4 to an Athlon 64, without requiring a clean (re-)install.
The SiS756 sits on the A9S sister board to provide the matching chipset for the Athlon 64. But we found it to be a cut-rate solution, because the HyperTransport bus on the A9S didn’t work at 1 GHz. The best we could do to achieve a stable 16-bit bus operation was 800 MHz.
