diff --git a/common.mk b/common.mk
index 1961873c..442c62f9 100644
--- a/common.mk
+++ b/common.mk
@@ -30,7 +30,7 @@ $(FIRRTL_JAR): $(call lookup_scala_srcs, $(CHIPYARD_FIRRTL_DIR)/src/main/scala)
 	touch $@
 
 #########################################################################################
-# create simulation args file rule
+# create list of simulation file inputs
 #########################################################################################
 $(sim_files): $(call lookup_scala_srcs,$(base_dir)/generators/utilities/src/main/scala) $(FIRRTL_JAR)
 	cd $(base_dir) && $(SBT) "project utilities" "runMain utilities.GenerateSimFiles -td $(build_dir) -sim $(sim_name)"
@@ -72,7 +72,7 @@ harness_macro_temp: $(HARNESS_SMEMS_CONF)
 	cd $(base_dir) && $(SBT) "project barstoolsMacros" "runMain barstools.macros.MacroCompiler -n $(HARNESS_SMEMS_CONF) -v $(HARNESS_SMEMS_FILE) -f $(HARNESS_SMEMS_FIR) $(HARNESS_MACROCOMPILER_MODE)"
 
 ########################################################################################
-# remove duplicate files in blackbox/simfiles
+# remove duplicate files and headers in list of simulation file inputs
 ########################################################################################
 $(sim_common_files): $(sim_files) $(sim_top_blackboxes) $(sim_harness_blackboxes)
 	awk '{print $1;}' $^ | sort -u | grep -v '.*\.h' > $@
diff --git a/variables.mk b/variables.mk
index b7ea0f7b..fca782fa 100644
--- a/variables.mk
+++ b/variables.mk
@@ -124,9 +124,11 @@ HARNESS_SMEMS_FILE ?= $(build_dir)/$(long_name).harness.mems.v
 HARNESS_SMEMS_CONF ?= $(build_dir)/$(long_name).harness.mems.conf
 HARNESS_SMEMS_FIR  ?= $(build_dir)/$(long_name).harness.mems.fir
 
+# files that contain lists of files needed for VCS or Verilator simulation
 sim_files                  ?= $(build_dir)/sim_files.f
 sim_top_blackboxes         ?= $(build_dir)/firrtl_black_box_resource_files.top.f
 sim_harness_blackboxes     ?= $(build_dir)/firrtl_black_box_resource_files.harness.f
+# single file that contains all files needed for VCS or Verilator simulation (unique and without .h's)
 sim_common_files           ?= $(build_dir)/sim_files.common.f
 
 #########################################################################################