diff --git a/.gitignore b/.gitignore
index 9c73c6e1..ab21150e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -26,3 +26,4 @@ project/metals.sbt
 project/project/
 .ivy2
 .sbt
+classpath-cache/
diff --git a/sims/vcs/Makefile b/sims/vcs/Makefile
index fc0a9fdb..8517fc1d 100644
--- a/sims/vcs/Makefile
+++ b/sims/vcs/Makefile
@@ -93,7 +93,7 @@ $(output_dir)/%.fsdb: $(output_dir)/% $(sim_debug)
 #########################################################################################
 .PHONY: clean clean-sim clean-sim-debug
 clean:
-	rm -rf $(gen_dir) $(sim_prefix)-* ucli.key
+	rm -rf $(CLASSPATH_CACHE) $(gen_dir) $(sim_prefix)-* ucli.key
 
 clean-sim:
 	rm -rf $(model_dir) $(build_dir)/vc_hdrs.h $(sim) $(sim).daidir ucli.key
diff --git a/sims/verilator/Makefile b/sims/verilator/Makefile
index 11b80331..dca1e414 100644
--- a/sims/verilator/Makefile
+++ b/sims/verilator/Makefile
@@ -226,7 +226,7 @@ $(output_dir)/%.vpd: $(output_dir)/% $(sim_debug)
 #########################################################################################
 .PHONY: clean clean-sim clean-sim-debug
 clean:
-	rm -rf $(gen_dir) $(sim_prefix)-*
+	rm -rf $(CLASSPATH_CACHE) $(gen_dir) $(sim_prefix)-*
 
 clean-sim:
 	rm -rf $(model_dir) $(sim)
diff --git a/sims/xcelium/Makefile b/sims/xcelium/Makefile
index 12b31087..41acdeec 100644
--- a/sims/xcelium/Makefile
+++ b/sims/xcelium/Makefile
@@ -131,7 +131,7 @@ $(output_dir)/%.vcd: $(output_dir)/% $(sim_debug)
 #########################################################################################
 .PHONY: clean clean-sim clean-sim-debug
 clean:
-	rm -rf $(gen_dir) $(sim_prefix)-*
+	rm -rf $(CLASSPATH_CACHE) $(gen_dir) $(sim_prefix)-*
 
 clean-sim:
 	rm -rf $(model_dir) $(sim) $(sim_workdir) $(sim_run_tcl) ucli.key bpad_*.err sigusrdump.out dramsim*.log
diff --git a/variables.mk b/variables.mk
index 35c947fc..86d26a72 100644
--- a/variables.mk
+++ b/variables.mk
@@ -146,8 +146,9 @@ ifeq ($(GENERATOR_PACKAGE),hwacha)
 endif
 
 # classpaths
-CHIPYARD_CLASSPATH ?= $(gen_dir)/chipyard.jar
-TAPEOUT_CLASSPATH ?= $(gen_dir)/tapeout.jar
+CLASSPATH_CACHE ?= $(base_dir)/classpath-cache
+CHIPYARD_CLASSPATH ?= $(CLASSPATH_CACHE)/chipyard.jar
+TAPEOUT_CLASSPATH ?= $(CLASSPATH_CACHE)/tapeout.jar
 # if *_CLASSPATH is a true java classpath, it can be colon-delimited list of paths (on *nix)
 CHIPYARD_CLASSPATH_TARGETS ?= $(subst :, ,$(CHIPYARD_CLASSPATH))
 TAPEOUT_CLASSPATH_TARGETS ?= $(subst :, ,$(TAPEOUT_CLASSPATH))
diff --git a/vlsi/Makefile b/vlsi/Makefile
index 8ca74d31..b3901fe6 100644
--- a/vlsi/Makefile
+++ b/vlsi/Makefile
@@ -171,4 +171,4 @@ $(OBJ_DIR)/hammer.d: $(HAMMER_D_DEPS)
 #########################################################################################
 .PHONY: clean
 clean:
-	rm -rf $(VLSI_OBJ_DIR) hammer-vlsi*.log __pycache__ output.json $(GENERATED_CONFS) $(gen_dir) $(SIM_CONF) $(SIM_DEBUG_CONF) $(SIM_TIMING_CONF) $(POWER_CONF)
+	rm -rf $(VLSI_OBJ_DIR) hammer-vlsi*.log __pycache__ output.json $(GENERATED_CONFS) $(CLASSPATH_CACHE) $(gen_dir) $(SIM_CONF) $(SIM_DEBUG_CONF) $(SIM_TIMING_CONF) $(POWER_CONF)