I think I was able to trace the issue to a call from /usr/NX/lib/libcrypto.so
[root@nomachine-test ~]# ulimit -c unlimited
[root@nomachine-test ~]# sysctl -w kernel.core_uses_pid=1
kernel.core_uses_pid = 1
[root@nomachine-test ~]# /etc/NX/nxserver –start
Illegal instruction (core dumped)
[root@nomachine-test ~]# gdb /usr/NX/bin/nxserver.bin core.25682
warning: no loadable sections found in added symbol-file system-supplied DSO at 0x7fff2e0eb000
Core was generated by `/usr/NX/bin/nxserver.bin –start’.
Program terminated with signal 4, Illegal instruction.
#0 0x00002aff1247f53c in OPENSSL_ia32_cpuid () from /usr/NX/lib/libcrypto.so