I had no idea that non-Intel processors had boundary restricted byte operations. This certainly could mean general network speedup.
It ultimately turned out that certain device drivers were exposing a problem in the alignment handler. By accessing misaligned IP header fragments, the driver concerned was triggering an alignment exception within an atomic-critical section of kernel code, which was then resulting in the scheduler being called from within the alignment handler. Although the driver was later fixed to improve performance (by using only aligned data), the problem with the alignment handler itself did require fixing to prevent unwanted system crashes.