Index: /trunk/src/VBox/Frontends/VirtualBox/src/settings/machine/UIMachineSettingsSystem.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/settings/machine/UIMachineSettingsSystem.cpp	(revision 73156)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/settings/machine/UIMachineSettingsSystem.cpp	(revision 73157)
@@ -475,7 +475,22 @@
         if (m_pSliderCPUExecCap->value() < (int)m_uMedGuestCPUExecCap)
         {
-            message.second << tr(
-                "The processor execution cap is set to a low value. This may make the machine feel slow to respond.");
-        }
+            message.second << tr("The processor execution cap is set to a low value. This may make the machine feel slow to respond.");
+        }
+
+        /* Warn user about possible performance degradation and suggest lowering # of CPU assigned to the VM instead : */
+        if (m_pSliderCPUExecCap->value() < 100)
+        {
+            if(m_uMaxGuestCPU > 1 && m_pSliderCPUCount->value() > 1)
+            {
+                message.second << tr("Please consider lowering the number of CPU assigned to the virtual machine rather"
+                                     " than setting the processor execution cap");
+            }
+            else if (m_uMaxGuestCPU > 1)
+            {
+                message.second << tr("Lowering the processor execution cap may result in a decline in performance.");
+
+            }
+        }
+    }
 
         /* Serialize message: */