Over the course of the show, we've seen several motherboards based on the MCP55 chipset. We understand that this is the chip behind NVIDIA's nForce 500-series of chipset solutions.
After speaking to several motherboard makers, they told us that they needed to implement a dual chip solution in order to add additional onboard devices along with dual full-bandwidth PCI-Express x16 slots for two video cards operating in SLI mode.
The killer is that motherboard makers are using a C51 SPP and the MCP55 'South Bridge' in their dual X16 SLI motherboards for Socket AM2. There are single chip dual X8 solutions available from most makers that just use the MCP55 chip.
Details of the chipset are not confirmed yet and NVIDIA is unlikely to speak about this before Socket AM2 is launched. However, every board that we've seen based on the chipset has had six SATA II ports and a single IDE port. This appears to be a decision made by NVIDIA, as SATA optical drives are becoming more readily available and affordable.
While we were out in Santa Clara earlier this month, we saw both NVIDIA's nForce4 SLI X16 and ATI's CrossFire Xpress 3200 chipset running a PCI-Express bandwidth benchmark that proved NVIDIA's dual PCI-Express x16 implementation wasn't bandwidth limited at all - the scores were very similar on both chipsets.
Obviously, this means that motherboard makers have to cool two chips on the high end boards, but many of the boards we've seen have featured silent heatpipe cooling solutions.