shared memory multiprocessor

Shared memory multiprocessors have multiple CPUs all of which share the
same address space.  This means there is only one memory accessed
by all CPUs on an equal basis.  Shared memory systems can be either
SIMD or MIMD.  Single-CPU vectorprocessors can be regarded as an
example of the former, while the multi-CPU models of these machines are
examples of the latter.

The main problem with shared memory systems is the connection of
the CPUs to each other and to the memory.
Various interconnection alternatives have been used, including
crossbar, $\Omega$-network, and central databus.
The IBM SP2, the Meiko CS-2, and the Cenju-3 use the $\Omega$-network.

\cite{van-der-Steen-overview}