diff --git a/build/simh/boot b/build/simh/boot
index 270172d9..cb998543 100644
--- a/build/simh/boot
+++ b/build/simh/boot
@@ -2,5 +2,8 @@ set cpu its
 set cpu idle
 set tim y2k
 set rp0 rp06
+set xu ena
+set xu debug
+set debug stdout
 at rp0 out/rp0.dsk
 b rp0