diff --git a/numpy/_core/tests/test_scalar_methods.py b/numpy/_core/tests/test_scalar_methods.py
index 3cb00dc6ab64..6630e722b37d 100644
--- a/numpy/_core/tests/test_scalar_methods.py
+++ b/numpy/_core/tests/test_scalar_methods.py
@@ -3,7 +3,6 @@
 """
 import fractions
 import inspect
-import platform
 import sys
 import types
 from typing import Any, Literal
@@ -13,6 +12,7 @@
 import numpy as np
 from numpy._core import sctypes
 from numpy.testing import assert_equal, assert_raises
+from numpy.testing._private.utils import LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE
 
 
 class TestAsIntegerRatio:
@@ -87,7 +87,7 @@ def test_against_known_values(self):
                     np.finfo(np.double) == np.finfo(np.longdouble),
                     reason="long double is same as double"),
                 pytest.mark.skipif(
-                    platform.machine().startswith("ppc"),
+                    LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE,
                     reason="IBM double double"),
             ]
         )
diff --git a/numpy/_core/tests/test_scalarmath.py b/numpy/_core/tests/test_scalarmath.py
index 877ea8b8ffba..c465b90f85c7 100644
--- a/numpy/_core/tests/test_scalarmath.py
+++ b/numpy/_core/tests/test_scalarmath.py
@@ -23,6 +23,7 @@
     assert_raises,
     check_support_sve,
 )
+from numpy.testing._private.utils import LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE
 
 types = [np.bool, np.byte, np.ubyte, np.short, np.ushort, np.intc, np.uintc,
          np.int_, np.uint, np.longlong, np.ulonglong,
@@ -521,7 +522,7 @@ def test_int_from_infinite_longdouble(self):
 
     @pytest.mark.skipif(np.finfo(np.double) == np.finfo(np.longdouble),
                         reason="long double is same as double")
-    @pytest.mark.skipif(platform.machine().startswith("ppc"),
+    @pytest.mark.skipif(LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE,
                         reason="IBM double double")
     def test_int_from_huge_longdouble(self):
         # Produce a longdouble that would overflow a double,
diff --git a/numpy/_core/tests/test_scalarprint.py b/numpy/_core/tests/test_scalarprint.py
index 38ed7780f2e6..7d5ce3004dff 100644
--- a/numpy/_core/tests/test_scalarprint.py
+++ b/numpy/_core/tests/test_scalarprint.py
@@ -1,12 +1,12 @@
 """ Test printing of scalar types.
 
 """
-import platform
 
 import pytest
 
 import numpy as np
 from numpy.testing import IS_MUSL, assert_, assert_equal, assert_raises
+from numpy.testing._private.utils import LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE
 
 
 class TestRealScalars:
@@ -329,8 +329,8 @@ def test_dragon4_scientific_interface(self, tp):
         assert_equal(fsci(tp('1.0'), unique=False, precision=4),
                         "1.0000e+00")
 
-    @pytest.mark.skipif(not platform.machine().startswith("ppc64"),
-                        reason="only applies to ppc float128 values")
+    @pytest.mark.skipif(not LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE,
+                        reason="only applies to ppc double-double values")
     def test_ppc64_ibm_double_double128(self):
         # check that the precision decreases once we get into the subnormal
         # range. Unlike float64, this starts around 1e-292 instead of 1e-308,
diff --git a/numpy/_core/tests/test_umath.py b/numpy/_core/tests/test_umath.py
index b5f621c7927d..821837cd28da 100644
--- a/numpy/_core/tests/test_umath.py
+++ b/numpy/_core/tests/test_umath.py
@@ -31,7 +31,10 @@
     assert_raises,
     assert_raises_regex,
 )
-from numpy.testing._private.utils import _glibc_older_than
+from numpy.testing._private.utils import (
+    LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE,
+    _glibc_older_than,
+)
 
 UFUNCS = [obj for obj in np._core.umath.__dict__.values()
          if isinstance(obj, np.ufunc)]
@@ -4808,7 +4811,7 @@ def test_nextafterf():
 
 @pytest.mark.skipif(np.finfo(np.double) == np.finfo(np.longdouble),
                     reason="long double is same as double")
-@pytest.mark.xfail(condition=platform.machine().startswith("ppc64"),
+@pytest.mark.xfail(condition=LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE,
                     reason="IBM double double")
 def test_nextafterl():
     return _test_nextafter(np.longdouble)
@@ -4847,7 +4850,7 @@ def test_spacingf():
 
 @pytest.mark.skipif(np.finfo(np.double) == np.finfo(np.longdouble),
                     reason="long double is same as double")
-@pytest.mark.xfail(condition=platform.machine().startswith("ppc64"),
+@pytest.mark.xfail(condition=LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE,
                     reason="IBM double double")
 def test_spacingl():
     return _test_spacing(np.longdouble)
diff --git a/numpy/testing/_private/utils.py b/numpy/testing/_private/utils.py
index 4cd56cfc4fc4..43eb6a6dd85e 100644
--- a/numpy/testing/_private/utils.py
+++ b/numpy/testing/_private/utils.py
@@ -107,6 +107,10 @@ class KnownFailureException(Exception):
 NOGIL_BUILD = bool(sysconfig.get_config_var("Py_GIL_DISABLED"))
 IS_64BIT = np.dtype(np.intp).itemsize == 8
 
+LONG_DOUBLE_IS_IBM_DOUBLE_DOUBLE = (platform.machine().startswith("ppc")
+                                    and str(np.finfo(np.longdouble).max)
+                                    == "1.79769313486231580793728971405301e+308")
+
 def assert_(val, msg=''):
     """
     Assert that works in release mode.