diff --git a/sims/firesim b/sims/firesim
index 21475d1c..afad1b6a 160000
--- a/sims/firesim
+++ b/sims/firesim
@@ -1 +1 @@
-Subproject commit 21475d1c90500c01d3eb18a684831be93de6b089
+Subproject commit afad1b6accfaba5efbc0cfeea66372abae5ab2eb
diff --git a/vlsi/Makefile b/vlsi/Makefile
index bdbeb1bb..d7135bb5 100644
--- a/vlsi/Makefile
+++ b/vlsi/Makefile
@@ -28,11 +28,16 @@ ifeq ($(tech_name),asap7)
 else
 	MACROCOMPILER_MODE ?= -l $(SMEMS_CACHE) -hir $(SMEMS_HAMMER)
 endif
-OBJ_DIR            ?= $(vlsi_dir)/build
 ENV_YML            ?= $(vlsi_dir)/env.yml
 INPUT_CONFS        ?= example.yml
 HAMMER_EXEC        ?= ./example-vlsi
 VLSI_TOP           ?= $(TOP)
+VLSI_OBJ_DIR       ?= $(vlsi_dir)/build
+ifneq($(CUSTOM_VLOG), )
+	OBJ_DIR        ?= $(VLSI_OBJ_DIR)/custom-$(VLSI_TOP)
+else
+	OBJ_DIR        ?= $(VLSI_OBJ_DIR)/$(long_name)-$(VLSI_TOP)
+endif
 
 #########################################################################################
 # general rules
@@ -119,4 +124,4 @@ $(OBJ_DIR)/hammer.d: $(HAMMER_D_DEPS)
 #########################################################################################
 .PHONY: clean
 clean:
-	rm -rf $(OBJ_DIR) hammer-vlsi*.log __pycache__ output.json $(GENERATED_CONFS) $(gen_dir)
+	rm -rf $(VLSI_OBJ_DIR) hammer-vlsi*.log __pycache__ output.json $(GENERATED_CONFS) $(gen_dir)