Owner`s manual

The XMI is the 64-bitsystem bus that interconnects the processors, memory
modules, and I/O adapters.
The XMI bus uses the concept of a node. A node is a single functional unit
that consists of one or more modules. The XMI has three types of nodes:
processor nodes, memory nodes, and I/O adapters.
A processor node is a single-board scalar processor or a scalar/vector
processor pair. Multiprocessing is supported on VAX 6000 systems. Up
to six scalar processors can be used in most systems.
1
Models 400 and
500 support vector processing with multiple scalar/vector processor pairs.
Symmetric multiprocessing is supported, allowing a program to execute on
any processor.
In a multiprocessing system one scalarprocessorbecomesthe boot processor
during power-up, and that boot processor loads the operating system and
handles communication with the operator console. The other processors
become secondary processors and receive system information from the boot
processor (see Section 4.5).
A memory node is one memory module. Memory is a global resource
equally accessible by all processors on the XMI. A memory module can have
32, 64, or 128 Mbytes of memory and associated ECC and control logic. The
memories are automatically interleaved. An optional battery backup unit
protects memory in case of power failure. The system supports up to eight
memories.
I/O adapters are installed on the XMI bus (see Section 1.6). If your system
has a VAXBI, the DWMBB adapter is used to connect VAXBI I/O adapters
to the XMI bus. See Appendix D for information on VAXBI I/O adapters.
The DWMVA adapter provides an interface to the VMEbus.
1
Model 200 supports multiprocessing with up to four scalar processors.
The VAX 6000 Series System 1–5