“every x64 machine is a NUMA machines”  - False

“all dualcore+ AMD boxes are treated as NUMA”- False

Then what is considered as NUMA by Sql Server?

1)      Any real “NUMA hardware”**

·          Low-end NUMA check: SQL Server by default  ignores NUMA configuration when hardware NUMA has four or less CPUs*** and at least one node has only one CPU***.

·          All AMD64 machines use NUMA design so any m/c satisfying low end NUMA check above would be considered a NUMA box from Sql Server perspective

·          To override the low-end NUMA check use T8021

2)      Any soft NUMA configuration: 

·          You usually configure soft-NUMA when you have many CPUs and do not have real hardware NUMA (Done thru registry settings)

·          You can also use soft-NUMA to subdivide hardware NUMA nodes into smaller groups.

 And here's a useful bit from Jason:

How do I know if the hardware I am running on is NUMA?

o       You can look at hardware specs. Note, your hardware may be NUMA but may be configured to use interleaved memory. In that case Windows will not recognize it as NUMA and therefore SQL Server. One quick way to check this is that if you have only one memory node, then the hardware is configured as non-NUMA.  You can run the following query to find the number of memory nodes

Select distinct memory_node_id

From sys.dm_os_memory_clerks

Please contact your hardware vendor to find out how to enable NUMA at hardware level.

o       During startup SQL Server will configure itself based on underlying OS and hardware configuration.  It will create the environment inside of itself  to mimic the actual hardware - SQL Server will create a software abstraction, for purpose of our discussion we will call it a Node, around every NUMA node and its memory.

You can look at errorlog to see if it has been booted with multiple NUMA nodes. Here is an example of the NUMA specific information with two nodes and with 1 CPU per node.

2005-09-13 16:08:49.23 Server      Multinode configuration: node 0: CPU mask: 0x00000002 Active CPU mask: 0x00000002. This message provides a description of the NUMA configuration for this computer. This is an informational message only. No user action is required.

2005-09-13 16:08:49.23 Server      Multinode configuration: node 1: CPU mask: 0x00000001 Active CPU mask: 0x00000001. This message provides a description of the NUMA configuration for this computer. This is an informational message only. No user action is required

o       Not all versions of SQL Server are NUMA aware. If you don't have SQL2000 post SP3 QFE that has NUMA optimizations you shouldn't be running SQL Server on the pure NUMA configuration. You may want to configure your system for interleaved memory. In general, SQL2000 has very limited set of NUMA optimizations and we recommend you to use SQL2005 to take full advantage of NUMA configuration.

o       Note that the NUMA Node id assigned by SQL may not match the Node id assigned by Windows.  SQL normally tries to boot on the non-default node (a NUMA Node other than Node 0).

**NUMA hardware has more than one system bus, each serving a small set of processors. Each group of processors has its own memory and possibly its own I/O channels, but each CPU can access memory associated with other groups in a coherent way. Each group is called a NUMA node                                                                              

***CPU being the logical representation so [1 socket with 1 core and no HT will be 1 CPU] and [1 socket with 2 cores and no HT will be 2 CPUs] and [1 socket with 1 core and HT enabled will be 2 CPUs] and so forth