Sun4d

Sun4d is a computer architecture introduced by Sun Microsystems in 1992. It is a development of the earlier Sun-4 architecture, using the XDBus system bus, SuperSPARC processors, and SBus I/O cards. The XDBus was the result of a collaboration between Sun and Xerox; its name comes from an earlier Xerox project, the Xerox Dragon. These were Sun's largest machines to date, and their first attempt at making a mainframe-class server.

Sun4d computers are true SMP systems; although memory and CPUs are installed per system board, the memory on a given board is not in any way "closer" to the CPUs on that same board. All memory and I/O devices are equally connected to all CPUs.

All of these computers use a passive backplane into which system boards are plugged. Each system board provides CPUs, memory, and an I/O bus. As system boards are added, these components are added to the whole in a completely seamless fashion. It is not a cluster, but works as a single large machine.

Sun4d computers include the SPARCcenter 2000 (1992) and SPARCserver 1000 (1993) from Sun Microsystems, and the Cray CS6400 (1993) from Cray Research. The system boards in these three machines are all slightly different, physically and electronically, and are not interchangeable.

All Sun4d machines provide JTAG ports, although unlike later systems the SPARCcenter and SPARCserver only use it for maintenance purposes.

The SPARCserver 1000 is a 5U rackmountable chassis with four 40 MHz XDBus slots, and space for four half-height 3.5" SCSI drives plus two half-height front-accessible 5.25" SCSI drives (typically used for CD-ROM and DAT). Each system board connects to one XDBus and provides two MBus slots for CPUs, three SBus slots for I/O boards, four banks of memory (four SIMMs apiece), and builtin SCSI-2, 10baseT Ethernet, and two serial ports.

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