diff --git a/sims/common-sim-flags.mk b/sims/common-sim-flags.mk
index d305d392..7c6c580d 100644
--- a/sims/common-sim-flags.mk
+++ b/sims/common-sim-flags.mk
@@ -23,16 +23,4 @@ SIM_LDFLAGS = \
 	$(EXTRA_SIM_LDFLAGS)
 
 SIM_FILE_REQS += \
-	$(TESTCHIP_RSRCS_DIR)/testchipip/csrc/SimSerial.cc \
-	$(TESTCHIP_RSRCS_DIR)/testchipip/csrc/SimDRAM.cc \
-	$(TESTCHIP_RSRCS_DIR)/testchipip/csrc/testchip_tsi.cc \
-	$(TESTCHIP_RSRCS_DIR)/testchipip/csrc/testchip_tsi.h \
-	$(TESTCHIP_RSRCS_DIR)/testchipip/csrc/mm.h \
-	$(TESTCHIP_RSRCS_DIR)/testchipip/csrc/mm.cc \
-	$(TESTCHIP_RSRCS_DIR)/testchipip/csrc/mm_dramsim2.h \
-	$(TESTCHIP_RSRCS_DIR)/testchipip/csrc/mm_dramsim2.cc \
-	$(ROCKETCHIP_RSRCS_DIR)/vsrc/EICG_wrapper.v \
-	$(ROCKETCHIP_RSRCS_DIR)/csrc/SimDTM.cc \
-	$(ROCKETCHIP_RSRCS_DIR)/csrc/SimJTAG.cc \
-	$(ROCKETCHIP_RSRCS_DIR)/csrc/remote_bitbang.h \
-	$(ROCKETCHIP_RSRCS_DIR)/csrc/remote_bitbang.cc
+	$(ROCKETCHIP_RSRCS_DIR)/vsrc/EICG_wrapper.v
diff --git a/sims/vcs/Makefile b/sims/vcs/Makefile
index a268c3ce..f0fc90e5 100644
--- a/sims/vcs/Makefile
+++ b/sims/vcs/Makefile
@@ -37,7 +37,7 @@ debug: $(sim_debug)
 SIM_FILE_REQS += \
 	$(ROCKETCHIP_RSRCS_DIR)/vsrc/TestDriver.v
 
-# ignore *.h files since vcs has +incdir
+# copy files but ignore *.h files in *.f since vcs has +incdir+$(build_dir)
 $(sim_files): $(SIM_FILE_REQS)
 	mkdir -p $(dir $(sim_files))
 	cp -f $^ $(build_dir)
diff --git a/sims/verilator/Makefile b/sims/verilator/Makefile
index 1cb3cf86..9c8f3fa6 100644
--- a/sims/verilator/Makefile
+++ b/sims/verilator/Makefile
@@ -50,7 +50,7 @@ SIM_FILE_REQS += \
 	$(CHIPYARD_RSRCS_DIR)/csrc/emulator.cc \
 	$(ROCKETCHIP_RSRCS_DIR)/csrc/verilator.h
 
-# add -FI for *.h files
+# copy files and add -FI for *.h files in *.f
 $(sim_files): $(SIM_FILE_REQS)
 	mkdir -p $(dir $(sim_files))
 	cp -f $^ $(build_dir)