Silicon Graphics SGI Altix 3700 Bx2, User Manual

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System Architecture
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System Architecture
The Altix 3700 Bx2 computer system is based on a distributed shared memory (DSM)
architecture. The system uses a global-address-space, cache-coherent multiprocessor that
scales to 64 Intel Itanium 2 processors in a single rack. Because it is modular, the DSM
combines the advantages of low entry cost with the ability to scale processors, memory,
and I/O independently to a maximum of 256 processors on a single-system image (SSI)
at initial release. Larger SSI configurations may be offered in the future, contact your SGI
sales or service representative for information.
The system architecture for the Altix 3700 Bx2 system is a fourth-generation NUMAflex
DSM architecture known as NUMAlink-4. In the NUMAlink-4 architecture, all
processors and memory are tied together into a single logical system with special
crossbar switches (routers). This combination of processors, memory, and crossbar
switches constitute the interconnect fabric called NUMAlink. There are two router
switches in each CR-brick.
The basic building block for the NUMAlink interconnect is the CR-brick. A CR-brick
contains up to four processor nodes; each processor node consists of a Super-Hub (SHub)
ASIC and two 64-bit processors with three levels of on-chip secondary caches. The two
Intel 64-bit processors are connected to the SHUB ASIC via a single high-speed front side
bus.
The SHub ASIC is the heart of the CR-brick. This specialized ASIC acts as a crossbar
between the processors, local SDRAM memory, the network interface, and the I/O
interface. The SHub ASIC memory interface enables any processor in the system to
access the memory of all processors in the system. Its I/O interface connects processors
to system I/O, which allows every processor in a system direct access to every I/O slot
in the system.
Another component of the NUMAlink-4 architecture is the router ASIC. The router ASIC
is a custom designed 8-port crossbar ASIC in the CR-brick. Using the router ASICs with
highly specialized NUMAlink-4 cables provides a high-bandwidth, extremely
low-latency interconnect between all CR-bricks in the system. This interconnection can
create a single contiguous system memory of up to 6 TB (terabytes) for a 512 processor
system.
Figure 3-3 on page 50 shows a functional block diagram of the Altix 3700 Bx2 series
system CR-brick including nodes, routers, and other major components.