--- wikisrc/ports.mdwn	2018/10/26 21:19:13	1.18
+++ wikisrc/ports.mdwn	2018/11/11 16:31:56	1.20
@@ -139,3 +139,15 @@ sparc64		|I		|[[sparc64]] (Can also run 
 vax		|II		|[[vax]]
 x86_64		|I		|[[amd64]] (Can also run i386 binaries), xen
 """]]
+
+## Various ways of denoting ports and CPUs
+
+When discussing ports and CPUs, there are two concepts, each of which have three ways of being named.  Strictly, the word port refers to the value shown by "uname -m", and typically corresponds to a directory under src/sys.  build.sh supports aliases, which are passed as if they were a port, but expand to a port and a cpu (MACHINE and MACHINE_ARCH); an example is evbearmv7hf-el which expands to the evbarm port and earmv7hf cpu.
+
+[[!table data="""
+concept | /usr/share/mk variable | uname | build.sh
+port | MACHINE      | uname -m | build.sh -m
+cpu  | MACHINE_ARCH | uname -p | build.sh -a
+"""]]
+
+Additonally, there are things referred to as ports which are not actually "uname -m" values, but are notably different than what would be expected from that port name.  One is xen, which is a system architecture variant of i386/amd64, and aarch64, which is CPU type variant of evbarm.