Placer is the Intel codename for a dual channel 133 MHz system bus DDR system (two PC266 DDR channels, 533 MHz system bus) for the Xeon 2-way workstations.
It includes PCI-X support, AGP 8x support and SATA support. Initially it will ship for Xeons only, but within a few weeks you can expect a Pentium 4 desktop/workstation and Xeon server version (whose codenames I forget).
It’s based on the same design as the E7500 chipset for dual channel PC200 DDR and a 400 MHz system bus of 2-way Xeon servers. The Xeon server version will sport additional PCI-X busses in leiu of AGP 8x, and the Pentium 4 desktop version will likely sport more 32 bit 33 MHz PCI slots and many boards may lack PCI-X support entirely.
The Placer chipset and its derivatives will replace the E7500, i860 and i850 chipsets in the 2-way server, 2-way workstation and 2-way desktop/workstation areas, respectively.