It is probably of note that 6400 was not supercomputer per-se but Cray's attempt to produce bussines oriented mainframe. It was SPARC based more or less sun4d m

It is probably of note that 6400 was not supercomputer per-se but Cray's attempt to produce bussines oriented mainframe. It was SPARC based more or less sun4d machine. As it did not exactly fit into SGI's lineup, after the SGI aquisition it was quickly sold to Sun who then made larger UltraSPARC based variant known as Enterprise 10000. From the technical perspective it is a large single system image multiprocessor system running solaris with hardware support for logical partitioning (which famously involves configuring the backplane logic through JTAG from attached sun4 machine with somewhat non-trivial software).