C H A P T E R 3

Hardware Overview

The Sun Fire systems are a family of symmetrical shared-memory multiprocessors (SMPs).

You can view the Sun Fire systems at several functions of detail:

Standard operation (simple SMP, OS functions)

Interconnect (details of interconnect for OS boot and RAS features)

Console bus interconnect (details of how the System Controller board controls the system)

3.1 Standard Operation

The standard operation is simply that of an SMP running an operating system with standard functions. It consists of CPU/Memory devices and I/O devices connected through an interconnect bus. Although the data interconnect is actually a crossbar switch, it is logically a bus. This is illustrated in FIGURE 3-1.

FIGURE 3-1 Standard Operation of the Sun Fire 6800/4810/4800/3800 Systems

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3.2 Data Interconnect

Although the standard operation of the Sun Fire system is that of a simple "bus-like" interconnect, it is actually a point-to-point switched interconnect, with two levels of repeaters or switches.

The switch is capable of complex functions such as:

Dividing the system into completely isolated partitions

Dividing the partition into logically isolated domains

To boot the operating system and to exercise the functions listed above, the system controller needs to be aware of the logical structure of the switch interconnect.

The Sun Fire 6800 system has six slots for CPU/Memory boards. The Sun Fire 4810/4800 systems have three slots for CPU/Memory boards. The Sun Fire 3800 system has two slots for CPU/Memory boards. Each CPU/Memory board has up to four UltraSPARC III 750-MHz or UltraSPARC III 900-MHz CPUs. The CPU also includes a memory controller, and each CPU can support one memory bank with up to eight DIMMs.

The Sun Fire 6800 system has four bays for the I/O assemblies. Two bays are included in the Sun Fire 4810/4800/3800 systems for I/O assemblies. The Sun Fire 6800/4810/4800 systems support both PCI and CompactPCI I/O chassis. The Sun Fire 3800 system has two bays for CompactPCI only I/O chassis. Each PCI I/O assembly has two I/O controllers, each with one 66-MHz PCI bus and one 33-MHz PCI bus.

The Sun Fire 6800 system is designed to greatly improve reliability, serviceability, and availability (RAS) over previous generations of systems. The Sun Fire system is designed to be able to recover from any hardware failure. Some failure recovery will not impact users (for example, a power supply failure) if the system is configured for redundant power supplies. Some failure recovery (for example, a CPU failure) will require a reboot, and will impact users, but a properly configured system will always be able to recover from any hardware failure.

The address path and data path are treated in slightly different ways. The address path has two completely redundant repeaters. A complete address repeater path requires two Repeater boards, as the Address Repeater (AR) function is bit-sliced across two ARs. On the Sun Fire 6800 system, the data path is bit-sliced across all four Repeater boards for standard operation. Optionally, a single pair of Repeater boards can be used in "double-pumped" mode, so that full functionality, although with lowered data bandwidth, is retained.

The Repeater boards have active devices. Because centerplanes are relatively hard to service, the Sun Fire 6800/4810/4800 systems were designed so that no active devices are present on the centerplane. The Sun Fire 3800 system, however, incorporates all the active components onto its centerplane.

3.3 Console Bus Interconnect

The console bus enables the system controllers to read and write registers on the rest of the system. Only one of the two SCs can be master on the console bus at a time. Each system controller is connected to a console bus hub (CBH), and the two CBHs arbitrate for the use of the console bus.