DS sells two CPU support chipsets. The 2107x chipset (aka APECS) is a 21064(A) support chiset. The 2117x chipset (aka ALCOR) is a 21164 support chipset. There will also be 2117xA chipset (aka ALCOR 2) as a 21164A support chipset.
Both chipsets provide memory controllers and PCI host bridges for their CPU. APECS provides a 32-bit PCI host bridge, ALCOR provides a 64-bit PCI host bridge which (in accordance with the requirements of the PCI spec) can support both 32-bit and 64-bit PCI devices.
APECS consists of 6, 208-pin chips (4, 32-bit data slices (DECADE), 1 system controller (COMANCHE), 1 PCI controller (EPIC)). It provides a DRAM controller (128-bit memory bus) and a PCI interface. It also does all the work to maintain memory coherence when a PCI device DMAs into (or out of) memory.
ALCOR consists of 5 chips (4, 64-bit data slices (Data Switch, DSW) - 208-pin PQFP and 1 control (Control, I/O Address, CIA) - a 383 pin plastic PGA). It provides a DRAM controller (256-bit memory bus) and a PCI interface. It also does all the work required to support an external Bcache and to maintain memory coherence when a PCI device DMAs into (or out of) memory.
There is no support chipset for the 21066, since the memory controller and PCI host bridge functionality are integrated onto the chip.