diff --git a/pymlac/Makefile b/pymlac/Makefile
index 8fce8a6..faaf991 100644
--- a/pymlac/Makefile
+++ b/pymlac/Makefile
@@ -7,17 +7,18 @@ test:
 	pymlac -b ptr -c -ptr dumpmem_test.ptp -t 040,045:050,052:055,060:065,066:071,077:0100,0110:03700,03761:03766,03777 -r 040 -r 0100
 
 test_debug:	
-	rm -f test.ptr test.ptp CPU.test.trace test_CPU.log
-	./make_ptr > test.ptr
-	python test_CPU.py CPU.test
-	#python test_Display.py     # interactive!
-	@echo "##########  Run 'python test_Display.py' by hand!  ##########"
-	#python test_KBD.py                # interactive!
-	@echo "##########  Run 'python test_KBD.py' by hand!  ##########"
-	python test_Memory.py
-	python test_PTR_PTP.py
-	python test_TTYIN.py
-	python test_TTYOUT.py
+	rm -f test.ptr test.ptp CPU.test.trace test_CPU.log pymlac.trace
+	python test_CPU.py dumpmem.test
+#	./make_ptr > test.ptr
+#	python test_CPU.py CPU.test
+#	#python test_Display.py     # interactive!
+#	@echo "##########  Run 'python test_Display.py' by hand!  ##########"
+#	#python test_KBD.py                # interactive!
+#	@echo "##########  Run 'python test_KBD.py' by hand!  ##########"
+#	python test_Memory.py
+#	python test_PTR_PTP.py
+#	python test_TTYIN.py
+#	python test_TTYOUT.py
 
 
 %:	%.ptp
diff --git a/pymlac/test_CPU.py b/pymlac/test_CPU.py
index 2ac2d8f..e4233ae 100644
--- a/pymlac/test_CPU.py
+++ b/pymlac/test_CPU.py
@@ -276,8 +276,11 @@ class TestCPU(object):
 
         self.used_cycles= 0
         while self.cpu.running:
-            cycles = self.cpu.execute_one_instruction()
-            trace.itraceend(False)
+            (cycles, tracestr) = self.cpu.execute_one_instruction()
+            if tracestr:
+                endstr = trace.itraceend(False)
+                trace.comment('%s\t%s' % (tracestr, endstr))
+                trace.flush()
             self.ptrptp.ptr_tick(cycles)
             self.ptrptp.ptp_tick(cycles)
             self.used_cycles += cycles
@@ -426,8 +429,8 @@ class TestCPU(object):
             if len(s) != 2:
                 return "dumpmem: dump limits are bad: %s" % addresses
             (begin, end) = s
-            begin = str2int(begin)
-            end = str2int(end)
+            begin = self.str2int(begin)
+            end = self.str2int(end)
             if begin is None or end is None:
                 return "dumpmem: dump limits are bad: %s" % addresses
 
@@ -625,7 +628,7 @@ class TestCPU(object):
             print(test)
             print('\t' + '\n\t'.join(result))
 
-        self.memdump('core.txt', 0, 0200)
+        self.memdump('core.txt', 03700, 0100)
 
     def memdump(self, filename, start, number):
         """Dump memory from 'start' into 'filename', 'number' words dumped."""