See https://github.com/MagicStack/uvloop/issues/576

diff -upr a/tests/test_pipes.py b/tests/test_pipes.py
--- a/tests/test_pipes.py	2023-10-22 22:53:42.000000000 +0200
+++ b/tests/test_pipes.py	2023-11-06 15:40:09.265497762 +0100
@@ -2,6 +2,8 @@ import asyncio
 import io
 import os
 import socket
+import unittest
+import platform
 
 from uvloop import _testbase as tb
 
@@ -248,6 +250,9 @@ class _BasePipeTest:
         self.loop.run_until_complete(proto.done)
         self.assertEqual('CLOSED', proto.state)
 
+    @unittest.skipIf(
+        platform.machine() == 'ppc64le',
+        'https://github.com/MagicStack/uvloop/issues/576')
     def test_write_buffer_full(self):
         rpipe, wpipe = os.pipe()
         pipeobj = io.open(wpipe, 'wb', 1024)
