1. A system comprising: an I/O device including: a local memory, wherein a portion of the local memory is mapped into a host memory address space as an I/O window cache, and a first snoop filter coupled to the local memory to filter a first plurality of snoop requests associated with the local memory; a system memory coupled to a controller hub, wherein a portion of the system memory is mapped into a local address space of the I/O device as an I/O device cache; and the controller hub coupled to the system memory through a memory interface and to the I/O device through a serial point-to-point interconnect, the controller hub to include a second snoop filter to filter a second plurality of snoop requests associated with the system memory.