diff --git a/javamds/mdsobjects.c b/javamds/mdsobjects.c
index 8cf411be12..f8d568f244 100644
--- a/javamds/mdsobjects.c
+++ b/javamds/mdsobjects.c
@@ -1441,7 +1441,11 @@ JNIEXPORT jobject JNICALL Java_MDSplus_Data_compile(JNIEnv *env,
   arglist[varIdx++] = &outXd;
   arglist[varIdx++] = MdsEND_ARG;
   *(int *)&arglist[0] = varIdx - 1;
+#ifdef MACOS_ARM64
+  status = (int)(intptr_t)LibCallgFfi(arglist, TdiCompile, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
   status = (int)(intptr_t)LibCallg(arglist, TdiCompile);
+#endif
   (*env)->ReleaseStringUTFChars(env, jexpr, expr);
   for (i = 0; i < numArgs; i++)
     FreeDescrip(arglist[2 + i]);
@@ -1553,7 +1557,11 @@ JNIEXPORT jobject JNICALL Java_MDSplus_Data_execute(JNIEnv *env,
   arglist[varIdx++] = &outXd;
   arglist[varIdx++] = MdsEND_ARG;
   *(int *)&arglist[0] = varIdx - 1;
+#ifdef MACOS_ARM64
+  status = (int)(intptr_t)LibCallgFfi(arglist, TdiCompile, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
   status = (int)(intptr_t)LibCallg(arglist, TdiCompile);
+#endif
   (*env)->ReleaseStringUTFChars(env, jexpr, expr);
   for (i = 0; i < numArgs; i++)
     FreeDescrip(arglist[2 + i]);
@@ -2235,7 +2243,11 @@ JNIEXPORT jobject JNICALL Java_MDSplus_Tree_compile(JNIEnv *env,
   arglist[varIdx++] = &outXd;
   arglist[varIdx++] = MdsEND_ARG;
   *(int *)&arglist[0] = varIdx - 1;
+#ifdef MACOS_ARM64
+  status = (int)(intptr_t)LibCallgFfi(arglist, _TdiCompile, VARIADIC_2_FIX_ARGS, RTN_INT32);
+#else
   status = (int)(intptr_t)LibCallg(arglist, _TdiCompile);
+#endif
   (*env)->ReleaseStringUTFChars(env, jexpr, expr);
   for (i = 0; i < numArgs; i++)
     FreeDescrip(arglist[3 + i]);
@@ -2291,7 +2303,11 @@ JNIEXPORT jobject JNICALL Java_MDSplus_Tree_execute(JNIEnv *env,
   arglist[varIdx++] = &outXd;
   arglist[varIdx++] = MdsEND_ARG;
   *(int *)&arglist[0] = varIdx - 1;
+#ifdef MACOS_ARM64
+  status = (int)(intptr_t)LibCallgFfi(arglist, _TdiExecute, VARIADIC_2_FIX_ARGS, RTN_INT32);
+#else
   status = (int)(intptr_t)LibCallg(arglist, _TdiExecute);
+#endif
   (*env)->ReleaseStringUTFChars(env, jexpr, expr);
   for (i = 0; i < numArgs; i++)
     FreeDescrip(arglist[3 + i]);
@@ -2331,7 +2347,11 @@ JNIEXPORT jobject JNICALL Java_MDSplus_Tree_data(JNIEnv *env,
   arglist[3] = &outXd;
   arglist[4] = MdsEND_ARG;
   *(int *)&arglist[0] = 4;
+#ifdef MACOS_ARM64
+  status = (int)(intptr_t)LibCallgFfi(arglist, _TdiData, VARIADIC_2_FIX_ARGS, RTN_INT32);
+#else
   status = (int)(intptr_t)LibCallg(arglist, _TdiData);
+#endif
   FreeDescrip(arglist[2]);
   if (STATUS_NOT_OK)
   {
@@ -2370,7 +2390,11 @@ JNIEXPORT jobject JNICALL Java_MDSplus_Tree_evaluate(JNIEnv *env,
   arglist[3] = &outXd;
   arglist[4] = MdsEND_ARG;
   *(int *)&arglist[0] = 4;
+#ifdef MACOS_ARM64
+  status = (int)(intptr_t)LibCallgFfi(arglist, _TdiEvaluate, VARIADIC_2_FIX_ARGS, RTN_INT32);
+#else
   status = (int)(intptr_t)LibCallg(arglist, _TdiEvaluate);
+#endif
   FreeDescrip(arglist[2]);
   if (STATUS_NOT_OK)
   {
diff --git a/mdslib/MdsLib.c b/mdslib/MdsLib.c
index 2f74566e8e..9e94bab625 100644
--- a/mdslib/MdsLib.c
+++ b/mdslib/MdsLib.c
@@ -30,6 +30,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <mdsshr.h>
 #include <stdint.h>
 #include <strroutines.h>
+#include <libroutines.h>
 static int MdsCONNECTION = -1;
 #define NDESCRIP_CACHE 1024
 #ifndef _CLIENT_ONLY
@@ -42,7 +43,6 @@ extern int TdiExecute(mdsdsc_t *, ...);
 extern int TdiCompile(mdsdsc_t *, ...);
 extern int TdiData(mdsdsc_t *, ...);
 extern int TdiCvt(mdsdsc_t *, ...);
-extern void *LibCallg();
 extern int TreeFindNode();
 extern int TreePutRecord();
 extern int TreeWait();
@@ -640,7 +640,11 @@ static inline int mds_value_vargs(va_list incrmtr, int connection,
     arglist[argidx++] = (void *)&xd1;
     arglist[argidx++] = MdsEND_ARG;
     *(int *)&arglist[0] = argidx - 1;
+#ifdef MACOS_ARM64
+    status = (int)(intptr_t)LibCallgFfi(arglist, TdiExecute, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
     status = (int)(intptr_t)LibCallg(arglist, TdiExecute);
+#endif
 
     if (STATUS_OK)
     {
@@ -898,7 +902,11 @@ static inline int mds_value2_vargs(va_list incrmtr, int connection,
     arglist[argidx++] = (void *)&xd1;
     arglist[argidx++] = MdsEND_ARG;
     *(int *)&arglist[0] = argidx - 1;
+#ifdef MACOS_ARM64
+    status = (int)(intptr_t)LibCallgFfi(arglist, TdiExecute, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
     status = (int)(intptr_t)LibCallg(arglist, TdiExecute);
+#endif
 
     if (STATUS_OK)
     {
@@ -1062,7 +1070,11 @@ static inline int mds_put_vargs(va_list incrmtr, int connection, char *pathname,
       arglist[argidx++] = MdsEND_ARG;
       *(int *)&arglist[0] = argidx - 1;
 
+#ifdef MACOS_ARM64
+      status = (int)(intptr_t)LibCallgFfi(arglist, TdiCompile, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
       status = (int)(intptr_t)LibCallg(arglist, TdiCompile);
+#endif
 
       if (STATUS_OK)
       {
@@ -1205,7 +1217,11 @@ static int mds_put2_vargs(va_list incrmtr, int connection, char *pathname,
       arglist[argidx++] = MdsEND_ARG;
       *(int *)&arglist[0] = argidx - 1;
 
+#ifdef MACOS_ARM64
+      status = (int)(intptr_t)LibCallgFfi(arglist, TdiCompile, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
       status = (int)(intptr_t)LibCallg(arglist, TdiCompile);
+#endif
 
       if (STATUS_OK)
       {
@@ -1334,7 +1350,11 @@ extern EXPORT int *cdescr(int dtype, void *data, ...)
   va_end(incrmtr);
   arglist[argidx++] = MdsEND_ARG;
   *(int *)&arglist[0] = argidx - 1;
+#ifdef MACOS_ARM64
+  status = (int)(intptr_t)LibCallgFfi(arglist, descr, VARIADIC_3_FIX_ARGS, RTN_INT32);
+#else
   status = (int)(intptr_t)LibCallg(arglist, descr);
+#endif
   return (&status);
 }
 #endif
diff --git a/mdslibidl/MdsLibIdl.c b/mdslibidl/MdsLibIdl.c
index 404e676f85..cd590e66f3 100644
--- a/mdslibidl/MdsLibIdl.c
+++ b/mdslibidl/MdsLibIdl.c
@@ -380,7 +380,11 @@ EXPORT int IdlMdsValue(int argc, void **argv)
   arglist[argidx++] = (void *)&tmp;
   arglist[argidx++] = MdsEND_ARG;
   *(long *)&arglist[0] = argidx;
+#ifdef MACOS_ARM64
+  status = (int)(intptr_t)LibCallgFfi(arglist, TdiExecute, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
   status = (int)(intptr_t)LibCallg(arglist, TdiExecute);
+#endif
   if (STATUS_OK)
   {
     status = TdiData(tmp.pointer, &mdsValueAnswer MDS_END_ARG);
@@ -626,7 +630,11 @@ EXPORT int IdlMdsPut(int argc, void **argv)
     arglist[argidx++] = (void *)&tmp;
     arglist[argidx++] = MdsEND_ARG;
     *(int *)&arglist[0] = argidx;
+#ifdef MACOS_ARM64
+    status = (int)(intptr_t)LibCallgFfi(arglist, TdiCompile, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
     status = (int)(intptr_t)LibCallg(arglist, TdiCompile);
+#endif
     if (STATUS_OK)
     {
       status = TreePutRecord(nid, (struct descriptor *)&tmp, 0);
diff --git a/mdsobjects/cpp/mdsdata.c b/mdsobjects/cpp/mdsdata.c
index 0ae3e82b9c..d33384d341 100644
--- a/mdsobjects/cpp/mdsdata.c
+++ b/mdsobjects/cpp/mdsdata.c
@@ -497,11 +497,19 @@ void *compileFromExprWithArgs(char *expr, int nArgs, void **args, void *tree,
 
   if (ctx)
   {
+#ifdef MACOS_ARM64
+    status = *retStatus = (int)(intptr_t)LibCallgFfi(arglist, _TdiCompile, VARIADIC_2_FIX_ARGS, RTN_INT32);
+#else
     status = *retStatus = (int)(intptr_t)LibCallg(arglist, _TdiCompile);
+#endif
   }
   else
   {
+#ifdef MACOS_ARM64
+    status = *retStatus = (int)(intptr_t)LibCallgFfi(arglist, TdiCompile, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
     status = *retStatus = (int)(intptr_t)LibCallg(arglist, TdiCompile);
+#endif
   }
   if (STATUS_NOT_OK)
     return NULL;
diff --git a/mdsobjects/cpp/mdsobjects.c b/mdsobjects/cpp/mdsobjects.c
index 170c98a9a2..ac66458d42 100644
--- a/mdsobjects/cpp/mdsobjects.c
+++ b/mdsobjects/cpp/mdsobjects.c
@@ -987,7 +987,11 @@ JNIEXPORT jobject JNICALL Java_mdsdata_Data_compileWithArgs(
   arglist[varIdx++] = (struct descriptor *)&outXd;
   arglist[varIdx++] = MdsEND_ARG;
   *(int *)&arglist[0] = varIdx - 1;
+#ifdef MACOS_ARM64
+  LibCallgFffi(arglist, TdiCompile, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
   LibCallg(arglist, TdiCompile);
+#endif
   for (i = 0; i < argLen; i++)
     freeDescrip(arglist[2 + i]);
   (*env)->ReleaseStringUTFChars(env, jexpr, expr);
diff --git a/mitdevices/t4012.c b/mitdevices/t4012.c
index fe3c380d74..06a046dcc4 100644
--- a/mitdevices/t4012.c
+++ b/mitdevices/t4012.c
@@ -418,6 +418,7 @@ static int ReadChannel(InStoreStruct * setup, int chunk, int samples, unsigned s
   return status;
 }
 
+// Usually called without a function, but once is called with TdiData().
 static int AccessTraq(InStoreStruct * setup, int data, int memsize, void *arglist,
 		      int (*routine) (struct descriptor *,...))
 {
@@ -434,7 +435,12 @@ static int AccessTraq(InStoreStruct * setup, int data, int memsize, void *arglis
   for (try = 0; (try < 30) && (!(CamQ(0) & 1)) && (STATUS_OK); try++) {
     if (arglist && !called) {
       called = 1;
+#ifdef MACOS_ARM64
+      // Only called with TdiData() which is an intrinsic thus RTN_INT32
+      LibCallgFfi(arglist, routine, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
       LibCallg(arglist, routine);
+#endif
     } else
       DevWait((float).001);
     piomem(17, 0, &data, memsize);
@@ -442,7 +448,11 @@ static int AccessTraq(InStoreStruct * setup, int data, int memsize, void *arglis
   if (try == 30)
     status = DEV$_CAM_NOSQ;
   if (arglist && !called)
+#ifdef MACOS_ARM64
+    LibCallgFfi(arglist, routine, VARIADIC_1_FIX_ARGS, RTN_INT32);
+#else
     LibCallg(arglist, routine);
+#endif
   return status;
 }
 
diff --git a/tdishr/TdiDoTask.c b/tdishr/TdiDoTask.c
index c4fa1d87f5..4ae3ebf385 100644
--- a/tdishr/TdiDoTask.c
+++ b/tdishr/TdiDoTask.c
@@ -96,7 +96,11 @@ static int Doit(struct descriptor_routine *ptask,
     status = TdiData(pmethod->method, &method_d MDS_END_ARG);
     if (STATUS_OK)
       status = TdiGetNid(pmethod->object, &nid);
+#ifdef MACOS_ARM64
+    status = (int)(intptr_t)LibCallgFfi(arglist, TreeDoMethod, VARIADIC_2_FIX_ARGS, RTN_INT32);
+#else
     status = (int)(intptr_t)LibCallg(arglist, TreeDoMethod);
+#endif
     FREED_NOW(&method_d);
     status = TdiPutLong(&status, out_ptr);
     break;
diff --git a/tdishr/TdiExtPython.c b/tdishr/TdiExtPython.c
index 07b9aa4cd4..186d1428a4 100644
--- a/tdishr/TdiExtPython.c
+++ b/tdishr/TdiExtPython.c
@@ -90,7 +90,11 @@ static int (*PyCallable_Check)() = NULL;
 static void (*PyErr_Clear)() = NULL;
 static PyObject *(*PyImport_AddModule)() = NULL;
 static PyObject *(*PyModule_AddObject)() = NULL;
+#ifdef MACOS_ARM64
+static PyObject *(*PyObject_CallFunctionObjArgs)(void *, ...) = NULL;
+#else
 static PyObject *(*PyObject_CallFunctionObjArgs)() = NULL;
+#endif
 static PyObject *(*PyString_FromString)() = NULL;
 // callPyFunction
 static PyObject *_Py_NoneStruct = NULL;
@@ -101,7 +105,11 @@ static int (*PyObject_IsSubclass)() = NULL;
 static void *(*PyLong_AsVoidPtr)() = NULL;
 static PyObject *(*PyObject_GetAttrString)() = NULL;
 // args_to_tuple
+#ifdef MACOS_ARM64
+static PyObject *(*PyObject_CallFunction)(void *, void *, ...) = NULL;
+#else
 static PyObject *(*PyObject_CallFunction)() = NULL;
+#endif
 static PyObject *(*PyTuple_New)() = NULL;
 static void (*PyTuple_SetItem)() = NULL;
 #ifdef USE_EXECFILE
@@ -129,7 +137,11 @@ inline static void initialize()
     _putenv_s("PyLib", envsym);
 #else
     envsym = "python2.7";
+#ifdef MACOS_ARM64
+    const char *aspath = "/opt/local/lib/libpython2.7.dylib";   // (MW) TODO: for MacPorts version
+#else 
     const char *aspath = "/usr/lib/python2.7.so.1";
+#endif
     setenv("PyLib", envsym, B_FALSE);
 #endif
     fprintf(stderr,
@@ -169,9 +181,15 @@ inline static void initialize()
     }
     else
     {
+    #ifdef MACOS_ARM64
+      lib = strcpy((char *)malloc(strlen(envsym) + 10), "lib");
+      strcat(lib, envsym);
+      strcat(lib, ".dylib");
+    #else
       lib = strcpy((char *)malloc(strlen(envsym) + 7), "lib");
       strcat(lib, envsym);
       strcat(lib, ".so");
+    #endif
     }
 #endif
     handle = dlopen(lib, RTLD_NOW | RTLD_GLOBAL);
diff --git a/treeshr/TreeDoMethod.c b/treeshr/TreeDoMethod.c
index dcfbd55add..4858bb88f3 100644
--- a/treeshr/TreeDoMethod.c
+++ b/treeshr/TreeDoMethod.c
@@ -171,6 +171,10 @@ int _TreeDoMethodA(void *dbid, mdsdsc_t *nid_dsc, mdsdsc_t *method_ptr,
       status = TdiINVDTYDSC;
       goto end;
     }
+    // MACOS_ARM64:  If the device calls a variadic function, then the call
+    // to _LibCallg() will segfault on Apple Silicon.   However, it is unlikely
+    // that Apple Silicon will be used for data acquistion servers (which are
+    // typically Linux).  Thus leaving this "as is" until bugs are reported.
     void (*addr)();
     status = LibFindImageSymbol(conglom_ptr->image, &method, &addr);
     if (STATUS_OK)