diff --git a/nac3artiq/artiq_builtins.py b/nac3artiq/artiq_builtins.py
index 55a11f0a..dc5c6eaa 100644
--- a/nac3artiq/artiq_builtins.py
+++ b/nac3artiq/artiq_builtins.py
@@ -1,20 +1,11 @@
-from language import *
 from numpy import int32, int64
 
-@extern
-def now_mu() -> int64:
-    raise NotImplementedError("syscall not simulated")
+from language import *
 
 
-@extern
-def at_mu(t: int64):
-    raise NotImplementedError("syscall not simulated")
-
-
-@extern
-def delay_mu(dt: int64):
-    raise NotImplementedError("syscall not simulated")
-
+import device_db
+if device_db.device_db["core"]["arguments"]["target"] == "cortexa9":
+	from artiq_timeline_extern import *
 
 @extern
 def rtio_init():
diff --git a/nac3artiq/artiq_timeline_extern.py b/nac3artiq/artiq_timeline_extern.py
new file mode 100644
index 00000000..fccf81ca
--- /dev/null
+++ b/nac3artiq/artiq_timeline_extern.py
@@ -0,0 +1,20 @@
+from numpy import int32, int64
+from language import *
+
+
+__all__ = ["now_mu", "at_mu", "delay_mu"]
+
+
+@extern
+def now_mu() -> int64:
+    raise NotImplementedError("syscall not simulated")
+
+
+@extern
+def at_mu(t: int64):
+    raise NotImplementedError("syscall not simulated")
+
+
+@extern
+def delay_mu(dt: int64):
+    raise NotImplementedError("syscall not simulated")