Do insist on seeing a full speed, fully functional example. For some reason MIPS chipsets operate under a curse, and over the last few years far more have been specified than have become real. Unless otherwise noted, all chipsets provide a memory controller and a PCI bus connection. A 64-bit variant is in the works. Used by router market leader Cisco, these are almost certainly the biggest-selling MIPS companion chips.
Online data is available.
There are now several variants of the smaller dipper, and a R5000 companion chip announced. Embedded systems suppliers Algorithmics are more active in the embedded systems world. Wind River Systems provide a real-time OS VxWorks for many MIPS CPUs. We have a soft spot for it because Algorithmics did the original port to the MIPS R4x00 architecture. We don't endorse any one of these products over the others, because our primary loyalty is to our customers and in most cases we have not used them in anger.