diff --git a/crosperf/machine_manager.py b/crosperf/machine_manager.py
index 0b38eef..aaf09bf 100644
--- a/crosperf/machine_manager.py
+++ b/crosperf/machine_manager.py
@@ -141,7 +141,12 @@
 
   def _ComputeMachineChecksumString(self):
     self.checksum_string = ''
-    exclude_lines_list = ['MHz', 'BogoMIPS', 'bogomips']
+    # Some lines from cpuinfo have to be excluded because they are not
+    # persistent across DUTs.
+    # MHz, BogoMIPS are dynamically changing values.
+    # core id, apicid are identifiers assigned on startup
+    # and may differ on the same type of machine.
+    exclude_lines_list = ['MHz', 'BogoMIPS', 'bogomips', 'core id', 'apicid']
     for line in self.cpuinfo.splitlines():
       if not any(e in line for e in exclude_lines_list):
         self.checksum_string += line
@@ -220,8 +225,8 @@
     self.logger = lgr or logger.GetLogger()
 
     if self.locks_dir and not os.path.isdir(self.locks_dir):
-      raise MissingLocksDirectory(
-          'Cannot access locks directory: %s' % self.locks_dir)
+      raise MissingLocksDirectory('Cannot access locks directory: %s' %
+                                  self.locks_dir)
 
     self._initialized_machines = []
     self.chromeos_root = chromeos_root
@@ -242,8 +247,8 @@
     ret, version, _ = self.ce.CrosRunCommandWOutput(
         cmd, machine=machine.name, chromeos_root=self.chromeos_root)
     if ret != 0:
-      raise CrosCommandError(
-          "Couldn't get Chrome version from %s." % machine.name)
+      raise CrosCommandError("Couldn't get Chrome version from %s." %
+                             machine.name)
 
     if ret != 0:
       version = ''
@@ -312,20 +317,33 @@
     # Since this is used for cache lookups before the machines have been
     # compared/verified, check here to make sure they all have the same
     # checksum (otherwise the cache lookup may not be valid).
-    common_checksum = None
+    base = None
     for machine in self.GetMachines(label):
       # Make sure the machine's checksums are calculated.
       if not machine.machine_checksum:
         machine.SetUpChecksumInfo()
-      cs = machine.machine_checksum
-      # If this is the first machine we've examined, initialize
-      # common_checksum.
-      if not common_checksum:
-        common_checksum = cs
+      # Use the first machine as the basis for comparison.
+      if not base:
+        base = machine
       # Make sure this machine's checksum matches our 'common' checksum.
-      if cs != common_checksum:
-        raise BadChecksum('Machine checksums do not match!')
-    self.machine_checksum[label.name] = common_checksum
+      if base.machine_checksum != machine.machine_checksum:
+        # Found a difference. Fatal error.
+        # Extract non-matching part and report it.
+        for mismatch_index in range(len(base.checksum_string)):
+          if (mismatch_index >= len(machine.checksum_string) or
+              base.checksum_string[mismatch_index] !=
+              machine.checksum_string[mismatch_index]):
+            break
+        # We want to show some context after the mismatch.
+        end_ind = mismatch_index + 8
+        # Print a mismatching string.
+        raise BadChecksum(
+            'Machine checksums do not match!\n'
+            'Diff:\n'
+            f'{base.name}: {base.checksum_string[:end_ind]}\n'
+            f'{machine.name}: {machine.checksum_string[:end_ind]}\n'
+            '\nCheck for matching /proc/cpuinfo and /proc/meminfo on DUTs.\n')
+    self.machine_checksum[label.name] = base.machine_checksum
 
   def ComputeCommonCheckSumString(self, label):
     # The assumption is that this function is only called AFTER
@@ -369,8 +387,8 @@
 
       if self.log_level != 'verbose':
         self.logger.LogOutput('Setting up remote access to %s' % machine_name)
-        self.logger.LogOutput(
-            'Checking machine characteristics for %s' % machine_name)
+        self.logger.LogOutput('Checking machine characteristics for %s' %
+                              machine_name)
       cm = CrosMachine(machine_name, self.chromeos_root, self.log_level)
       if cm.machine_checksum:
         self._all_machines.append(cm)
@@ -410,8 +428,8 @@
 
       if self.acquire_timeout < 0:
         self.logger.LogFatal('Could not acquire any of the '
-                             "following machines: '%s'" % ', '.join(
-                                 machine.name for machine in machines))
+                             "following machines: '%s'" %
+                             ', '.join(machine.name for machine in machines))
 
 
 ###      for m in self._machines:
@@ -664,8 +682,8 @@
       for m in self._all_machines:
         assert m.name != machine_name, 'Tried to double-add %s' % machine_name
       cm = MockCrosMachine(machine_name, self.chromeos_root, self.log_level)
-      assert cm.machine_checksum, (
-          'Could not find checksum for machine %s' % machine_name)
+      assert cm.machine_checksum, ('Could not find checksum for machine %s' %
+                                   machine_name)
       # In Original MachineManager, the test is 'if cm.machine_checksum:' - if a
       # machine is unreachable, then its machine_checksum is None. Here we
       # cannot do this, because machine_checksum is always faked, so we directly
diff --git a/crosperf/machine_manager_unittest.py b/crosperf/machine_manager_unittest.py
index 26eacbd..f47cc88 100755
--- a/crosperf/machine_manager_unittest.py
+++ b/crosperf/machine_manager_unittest.py
@@ -44,8 +44,8 @@
         assert m.name != machine_name, 'Tried to double-add %s' % machine_name
       cm = machine_manager.MockCrosMachine(machine_name, self.chromeos_root,
                                            'average')
-      assert cm.machine_checksum, (
-          'Could not find checksum for machine %s' % machine_name)
+      assert cm.machine_checksum, ('Could not find checksum for machine %s' %
+                                   machine_name)
       self._all_machines.append(cm)
 
 
@@ -87,9 +87,10 @@
   def setUp(self, mock_isdir):
 
     mock_isdir.return_value = True
-    self.mm = machine_manager.MachineManager(
-        '/usr/local/chromeos', 0, 'average', None, self.mock_cmd_exec,
-        self.mock_logger)
+    self.mm = machine_manager.MachineManager('/usr/local/chromeos', 0,
+                                             'average', None,
+                                             self.mock_cmd_exec,
+                                             self.mock_logger)
 
     self.mock_lumpy1.name = 'lumpy1'
     self.mock_lumpy2.name = 'lumpy2'
@@ -225,15 +226,14 @@
     self.assertEqual(mock_sleep.call_count, 0)
 
   def test_compute_common_checksum(self):
-
     self.mm.machine_checksum = {}
     self.mm.ComputeCommonCheckSum(LABEL_LUMPY)
     self.assertEqual(self.mm.machine_checksum['lumpy'], 'lumpy123')
     self.assertEqual(len(self.mm.machine_checksum), 1)
 
     self.mm.machine_checksum = {}
-    self.assertRaises(machine_manager.BadChecksum,
-                      self.mm.ComputeCommonCheckSum, LABEL_MIX)
+    self.assertRaisesRegex(machine_manager.BadChecksum, r'daisy.*\n.*lumpy',
+                           self.mm.ComputeCommonCheckSum, LABEL_MIX)
 
   def test_compute_common_checksum_string(self):
     self.mm.machine_checksum_string = {}
@@ -583,8 +583,8 @@
 CHECKSUM_STRING = ('processor: 0vendor_id: GenuineIntelcpu family: 6model: '
                    '42model name: Intel(R) Celeron(R) CPU 867 @ '
                    '1.30GHzstepping: 7microcode: 0x25cache size: 2048 '
-                   'KBphysical id: 0siblings: 2core id: 0cpu cores: 2apicid: '
-                   '0initial apicid: 0fpu: yesfpu_exception: yescpuid level: '
+                   'KBphysical id: 0siblings: 2cpu cores: 2'
+                   'fpu: yesfpu_exception: yescpuid level: '
                    '13wp: yesflags: fpu vme de pse tsc msr pae mce cx8 apic sep'
                    ' mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse '
                    'sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc '
@@ -597,8 +597,8 @@
                    'bits virtualpower management:processor: 1vendor_id: '
                    'GenuineIntelcpu family: 6model: 42model name: Intel(R) '
                    'Celeron(R) CPU 867 @ 1.30GHzstepping: 7microcode: 0x25cache'
-                   ' size: 2048 KBphysical id: 0siblings: 2core id: 1cpu cores:'
-                   ' 2apicid: 2initial apicid: 2fpu: yesfpu_exception: yescpuid'
+                   ' size: 2048 KBphysical id: 0siblings: 2cpu cores:'
+                   ' 2fpu: yesfpu_exception: yescpuid'
                    ' level: 13wp: yesflags: fpu vme de pse tsc msr pae mce cx8 '
                    'apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx '
                    'fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm '