IBM servers

#Symmetric multiprocessing (SMP)
Symmetric multiprocessing (SMP) designs are currently being challenged by the demand for
additional Intel processors within a single system. In SMP, CPUs have equal access to a
single, shared memory controller and memory space. Because processor speed has
dramatically increased to be much faster than memory, for most CPU intensive workloads the
single front-side bus and single memory controller are often a bottleneck, resulting in
excessive queuing delays and long memory latencies when under heavy load.
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#NUMA architecture
Non-uniform Memory Access (NUMA) is an architecture designed to improve performance
and solve latency problems inherent in large SMP systems with more than four processors.
By using this cache and providing fast local memory access to all processors, typical
bottlenecks that are associated with large SMP systems using a single memory controller
design are eliminated. Operating systems such as Windows 2000 perform well on this type of
architecture, but dramatic performance gains can be achieved when the operating system is
NUMA-aware, as with VMware ESX Server.