IHAC wrote to me that depend on which subnet he login to T5120 the timex sort file>file.out on /tmp give very different result;
one is about 8 sec
one is about 2. minute 50 sec
a factor of 21 difference.
Turnout that the locale is different in two way of login to the system one set LANG=C
one setto LNAG=en_US.utf8
the result for LANG=en_US is similar to LANG=C