diff --git a/compiler.mk b/compiler.mk
index 3fd3962..0128155 100644
--- a/compiler.mk
+++ b/compiler.mk
@@ -81,6 +81,9 @@ phase3_io_ficaa.svd: phase2_result.py phase3.py hexcalculator.py unroller.py rwo
 phase3_io_abindex.svd: phase2_result.py phase3.py hexcalculator.py unroller.py rwops.py settings.py
 	./phase3.py -a -m IO -d FCH::AB::ABIndex $< > $@.new && mv $@.new $@
 
+phase3_hostlegacy.svd: phase2_result.py phase3.py hexcalculator.py unroller.py rwops.py settings.py
+	./phase3.py -a -m HOSTLEGACY $< > $@.new && mv $@.new $@
+
 phase3_msr.svd: phase2_result.py phase3.py hexcalculator.py unroller.py rwops.py settings.py
 	./phase3.py -m MSR $< > $@.new && mv $@.new $@
 
diff --git a/phase3.py b/phase3.py
index 3275a51..b647f7b 100755
--- a/phase3.py
+++ b/phase3.py
@@ -107,8 +107,10 @@ elif selected_access_method == "SMN":
 		memory_map = []
 elif selected_access_method == "SMNCCD":
 	_, memory_map = getattr(phase2_result, "Memory_Map___SMNCCD_Physical_Mnemonic_Namespace", ("", []))
-elif selected_access_method == "IO":
-	memory_map = [] # TODO: fake all the IO things
+elif selected_access_method == "IO" or selected_access_method == "HOSTLEGACY":
+	memory_map = [] # TODO: hard-code all the IO namespaces
+elif selected_access_method == "HOSTLEGACY":
+	memory_map = []
 
 assert memory_map is not None, "Memory map for access_method={!r}, data_port_write={!r}".format(selected_access_method, selected_data_port_write)