From: karn@qualcomm.com (Phil Karn)
Date: Sun, 21 Feb 93 15:02:12 PST
To: hughes@soda.berkeley.edu
Subject: Re:  Trapdoors
Message-ID: <9302212253.AA14109@servo>
MIME-Version: 1.0
Content-Type: text/plain


A bit count instruction would be very handy in a project I've been
working on lately, which is a new packet radio link level protocol
for amateur packet radio. This protocol uses forward error correction,
so it needs a highly reliable way to delimit the start of each
physical link frame. A pseudo-random "sync" sequence is the standard
way to do this, and you detect it with a correlator. The bit count
instruction would come in handy here, since the only other fast
way to do it is to use table lookup.

Phil