nForce4, Anandtech Has The Details

[Aggressor Prime]

nVidia CK8-04 (nForce4) chipset, for Athlon 64 processors, is expected to be released in Late September. CK8-04 is the successor to the nForce3 Pro 250 on Socket 754 and the nForce3 Ultra MCP for Socket 939. The base CK8-04 will feature a 1Ghz HT link and is expected to feature 4 x SATA150 and 2 x ATA133 ports with full RAID capability between PATA and SATA, Gigabit Ethernet, 10 x USB2 ports, a hardware firewall and 20 PCI Express lanes (1 x 16 lane port and 4 x 1 lane ports in the base product). CK8-04 will also feature a replacement for the impressive SoundStorm audio built into the Socket A nForce chipsets. The replacement audio logic will be support High Definition 24bit, 96khz, 7.1 channel sound.
The more advanced Ultra version is also expected to feature SATA 300 support to replace the SATA 150 in the standard version and a Secure Networking Processor, which is intended to improve the security of your PC on a network and reduce network CPU overhead.
The final version of CK8-04 is the SLI version which is expected to feature a PCI Express switching chip, allowing either 1xPCI Express x16 port to be used for a single graphics card or 2xPCI Express x8 lanes (presumably with x16 interfaces) for dual graphics cards, e.g. for use with nVidia's SLI architecture built into the GeForce 6800 series and the GeForce 6600GT. A summary of the new chips follows:

nForce4 - 1Ghz HT, 4xSATA150, 2xATA133, 10xUSB2, Gigabit Ethernet, 7.1 audio.
nForce4 Ultra - 4xSATA300, Secure Networking Processor.
nForce4 SLI - PCI Express switching chip, allowing two graphics cards.

More here.

I can't wait to grab a nForce4 SLI motherboard.