diff --git a/idasm/check_sum.py b/idasm/check_sum.py
index 6958bd7..43ff07d 100644
--- a/idasm/check_sum.py
+++ b/idasm/check_sum.py
@@ -8,20 +8,28 @@ Test code to determine the checksum algorithm used in Imlac PTP blocks.
 MASK = 0177777
 
 # actual block from 40tp_simpleDisplay.ptp
-block = [065,       # word count
-         0000100,   # load address
-         0001012, 0102010, 0010101, 0002200, 0010103, 0001071, 0100041, 0044164,    # data words
-         0020111, 0000000, 0004116, 0001003, 0003100, 0010101, 0015000, 0025000,    # data words
-         0004005, 0006000, 0050132, 0050141, 0050151, 0050151, 0050156, 0015000,    # data words
-         0025000, 0000000, 0030303, 0141702, 0114230, 0143707, 0143203, 0100770,    # data words
-         0174171, 0030303, 0141702, 0154330, 0127655, 0174350, 0103605, 0154330,    # data words
-         0074571, 0030303, 0141702, 0000600, 0154330, 0074571, 0030202, 0141723,    # data words
-         0150327, 0143766, 0170362, 0074571, 0100000,                               # data words
-         0105226]   # checksum word
+block = [04,        # word count
+         0007700,   # load address
+         0001061, 0100011, 0023775, 0037765,    # data words
+         0165054
+        ]
+
+#block = [065,       # word count
+#         0000100,   # load address
+#         0001012, 0102010, 0010101, 0002200, 0010103, 0001071, 0100041, 0044164,    # data words
+#         0020111, 0000000, 0004116, 0001003, 0003100, 0010101, 0015000, 0025000,    # data words
+#         0004005, 0006000, 0050132, 0050141, 0050151, 0050151, 0050156, 0015000,    # data words
+#         0025000, 0000000, 0030303, 0141702, 0114230, 0143707, 0143203, 0100770,    # data words
+#         0174171, 0030303, 0141702, 0154330, 0127655, 0174350, 0103605, 0154330,    # data words
+#         0074571, 0030303, 0141702, 0000600, 0154330, 0074571, 0030202, 0141723,    # data words
+#         0150327, 0143766, 0170362, 0074571, 0100000,                               # data words
+#         0105226]   # checksum word
 
 def checksum1(block):
     """Checksum is sum of data words, mask at end."""
 
+    checksum1.tag = 'sum data, mask at end'
+
     checksum = 0
     for word in block[2:-1]:
         checksum += word
@@ -30,6 +38,8 @@ def checksum1(block):
 def checksum2(block):
     """Checksum is sum of data words, mask at each sum and end."""
 
+    checksum2.tag = 'sum data, mask each sum, mask at end'
+
     checksum = 0
     for word in block[2:-1]:
         checksum = (checksum + word) & MASK
@@ -38,6 +48,8 @@ def checksum2(block):
 def checksum3(block):
     """Checksum is sum of load address and data words, mask at end."""
 
+    checksum3.tag = 'sum loadaddr+data, mask at end'
+
     checksum = block[1]
     for word in block[2:-1]:
         checksum += word
@@ -46,6 +58,8 @@ def checksum3(block):
 def checksum4(block):
     """Checksum is sum of load address and data words, mask at each sum and end."""
 
+    checksum4.tag = 'sum loadaddr+data, mask each sum, mask at end'
+
     checksum = block[1]
     for word in block[2:-1]:
         checksum = (checksum + word) & MASK
@@ -55,6 +69,8 @@ def checksum5(block):
     """Checksum is sum of word count, load address and data words,
     mask at end."""
 
+    checksum5.tag = 'sum count+loadaddr+data, mask at end'
+
     checksum = block[0]
     checksum += block[1]
     for word in block[2:-1]:
@@ -65,6 +81,8 @@ def checksum6(block):
     """Checksum is sum of word count, load address and data words,
     mask at at each sum and end."""
 
+    checksum6.tag = 'sum count+loadaddr+data, mask each sum, mask at end'
+
     checksum = block[0]
     checksum = (checksum + block[1]) & MASK
     for word in block[2:-1]:
@@ -74,6 +92,8 @@ def checksum6(block):
 def checksum7(block):
     """Checksum is sum of data words, mask at end.  Sum is +1 on overflow"""
 
+    checksum7.tag = 'sum data, +1 on sum overflow, mask at end'
+
     checksum = 0
     for word in block[2:-1]:
         checksum += word
@@ -84,6 +104,8 @@ def checksum7(block):
 def checksum8(block):
     """Checksum is sum of load + data words, mask at end.  Sum is +1 on overflow"""
 
+    checksum8.tag = 'sum loadaddr+data, +1 on sum overflow, mask at end'
+
     checksum = block[1]
     for word in block[2:-1]:
         checksum += word
@@ -94,6 +116,8 @@ def checksum8(block):
 def checksum9(block):
     """Checksum is sum of count+load+data words, mask at end.  Sum is +1 on overflow"""
 
+    checksum9.tag = 'sum count+loadaddr+data, +1 on sum overflow, mask at end'
+
     checksum = block[0]
     checksum += block[1]
     if checksum & MASK:
@@ -114,14 +138,14 @@ csum7 = checksum7(block)
 csum8 = checksum8(block)
 csum9 = checksum9(block)
 
-print('csum1=%06o' % csum1)
-print('csum2=%06o' % csum2)
-print('csum3=%06o' % csum3)
-print('csum4=%06o' % csum4)
-print('csum5=%06o' % csum5)
-print('csum6=%06o' % csum6)
-print('csum7=%06o' % csum7)
-print('csum8=%06o' % csum8)
-print('csum9=%06o' % csum9)
+print('csum1=%06o, %s' % (csum1, checksum1.tag))
+print('csum2=%06o, %s' % (csum2, checksum2.tag))
+print('csum3=%06o, %s' % (csum3, checksum3.tag))
+print('csum4=%06o, %s' % (csum4, checksum4.tag))
+print('csum5=%06o, %s' % (csum5, checksum5.tag))
+print('csum6=%06o, %s' % (csum6, checksum6.tag))
+print('csum7=%06o, %s' % (csum7, checksum7.tag))
+print('csum8=%06o, %s' % (csum8, checksum8.tag))
+print('csum9=%06o, %s' % (csum9, checksum9.tag))
 
-print('checksum should be 105226')
+print('checksum should be %06o' % block[-1])