TestSocketIOWithTimeout uses a block size of 4192 bytes to simulate a partial write. This seems to be a valid in x86 architecture where the default minimum blocksize is 4096.
This testcase fails in PowerPC where the default minimum block size is 65536 bytes (64KB). So for PowerPC, using a blocksize little more than 64K , say 65555(65536 + 19) holds good for this scenario.
I attached a patch here where i made it very general by introducing NativeIO.POSIX.getCacheManipulator().getOperatingSystemPageSize() to get the page size.
I tested my patch in both ppc64 and x86 linux machines.