diff --git a/src/libCom/osi/os/WIN32/osdThread.c b/src/libCom/osi/os/WIN32/osdThread.c
index 70b9b53d2..c88b0e689 100644
--- a/src/libCom/osi/os/WIN32/osdThread.c
+++ b/src/libCom/osi/os/WIN32/osdThread.c
@@ -1110,7 +1110,11 @@ epicsShareFunc void * epicsShareAPI epicsThreadPrivateGet ( epicsThreadPrivateId
  */
 epicsShareFunc int epicsThreadGetCPUs ( void )
 {
-    return atoi(getenv("NUMBER_OF_PROCESSORS"));
+    SYSTEM_INFO sysinfo;
+    GetSystemInfo(&sysinfo);
+    if (sysinfo.dwNumberOfProcessors > 0)
+        return sysinfo.dwNumberOfProcessors;
+    return 1;
 }
 
 #ifdef TEST_CODES
diff --git a/src/libCom/osi/os/posix/osdThread.c b/src/libCom/osi/os/posix/osdThread.c
index 00fbdc936..18cc0b67b 100644
--- a/src/libCom/osi/os/posix/osdThread.c
+++ b/src/libCom/osi/os/posix/osdThread.c
@@ -875,5 +875,16 @@ epicsShareFunc double epicsShareAPI epicsThreadSleepQuantum ()
 
 epicsShareFunc int epicsThreadGetCPUs(void)
 {
-    return sysconf(_SC_NPROCESSORS_ONLN);
+    long ret;
+#ifdef _SC_NPROCESSORS_ONLN
+    ret = sysconf(_SC_NPROCESSORS_ONLN);
+    if (ret > 0)
+        return ret;
+#endif
+#ifdef _SC_NPROCESSORS_CONF
+    ret = sysconf(_SC_NPROCESSORS_CONF);
+    if (ret > 0)
+        return ret;
+#endif
+    return 1;
 }
diff --git a/src/libCom/test/epicsThreadTest.cpp b/src/libCom/test/epicsThreadTest.cpp
index b1e28bb8c..f80d3da7e 100644
--- a/src/libCom/test/epicsThreadTest.cpp
+++ b/src/libCom/test/epicsThreadTest.cpp
@@ -81,7 +81,11 @@ static void thread(void *arg)
 
 MAIN(epicsThreadTest)
 {
-    testPlan(8);
+    testPlan(9);
+
+    unsigned int ncpus = epicsThreadGetCPUs();
+    testDiag("System has %u CPUs", ncpus);
+    testOk1(ncpus > 0);
 
     const int ntasks = 3;
     myThread *myThreads[ntasks];