The SGI Origin family are large Unix servers using the MIPS processor. They are characterized by their massively insane scalability and I/O bandwidths.
The latest model, the Origin 3000, is designed around a modular set of "bricks", so you have different bricks which contain CPUs, RAM, PCI-X slots, etc. With the latest CPU modules, SGI can fit 128 CPUs and quarter of a terabyte of memory in a single rack. Older models were limited to 16 or 32 CPUs per rack.