diff --git a/lib/spack/llnl/util/cpu/microarchitectures.json b/lib/spack/llnl/util/cpu/microarchitectures.json
index 1ee782b408a784d7c5a803be5d59dd7c3074796b..2e20cc98f805bedb7947bd00ea6b3cf21b2b31eb 100644
--- a/lib/spack/llnl/util/cpu/microarchitectures.json
+++ b/lib/spack/llnl/util/cpu/microarchitectures.json
@@ -825,6 +825,41 @@
           "flags": "-march=armv8-a -mtune=generic"
         }
       }
+    },
+    "arm": {
+      "from": null,
+      "vendor": "generic",
+      "features": [],
+      "compilers": {
+      }
+    },
+    "ppc": {
+      "from": null,
+      "vendor": "generic",
+      "features": [],
+      "compilers": {
+      }
+    },
+    "ppcle": {
+      "from": null,
+      "vendor": "generic",
+      "features": [],
+      "compilers": {
+      }
+    },
+    "sparc": {
+      "from": null,
+      "vendor": "generic",
+      "features": [],
+      "compilers": {
+      }
+    },
+    "sparc64": {
+      "from": null,
+      "vendor": "generic",
+      "features": [],
+      "compilers": {
+      }
     }
   },
   "feature_aliases": {