diff --git a/src_Core/Core/CoreW.bsv b/src_Core/Core/CoreW.bsv
index 4bb29f2..eac3816 100644
--- a/src_Core/Core/CoreW.bsv
+++ b/src_Core/Core/CoreW.bsv
@@ -65,6 +65,18 @@ import TV_Taps  :: *;
 
 import DM_CPU_Req_Rsp ::*;
 
+// ================================================================
+// EXTERNAL_DEBUG_MODULE is used in situations where we DO NOTt have a
+// Debug Module controlling the CPU.  In that case, the CPU is
+// 'halted' by asserting the reset signal, during which the external
+// debugger can read/write memory etc.
+
+// EXTERNAL_DEBUG_MODULE and INCLUDE_GDB_CONTROL should never both be defined.
+
+`ifdef EXTERNAL_DEBUG_MODULE
+`undef INCLUDE_GDB_CONTROL
+`endif
+
 // ================================================================
 // The Core module
 
diff --git a/src_SSITH_P3/Makefile b/src_SSITH_P3/Makefile
index 9cc95fb..2722bf0 100644
--- a/src_SSITH_P3/Makefile
+++ b/src_SSITH_P3/Makefile
@@ -34,7 +34,10 @@ BSC_COMPILATION_FLAGS += \
 	-D INCLUDE_TANDEM_VERIF \
 	-D BRVF_TRACE \
 	-D XILINX_BSCAN  -D XILINX_XCVU9P  -D JTAG_TAP \
-	-D EXTERNAL_DEBUG_MODULE
+
+
+# Only used if we don't have INCLUDE_GDB_CONTROL
+#	-D EXTERNAL_DEBUG_MODULE
 
 #================================================================
 # Parameter settings for MIT RISCY