Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hpfcdc!hpldola!ppa
From: ppa@hpldola.HP.COM (Paul P. Austgen)
Newsgroups: comp.sys.ibm.pc
Subject: Re: RLL/Floppy controller advice wanted
Message-ID: <11250081@hpldola.HP.COM>
Date: 13 Jun 89 15:00:32 GMT
References: <3375@cps3xx.UUCP>
Organization: HP Elec. Design Div. -ColoSpgs
Lines: 10

These are different coding methods for writing data onto the disc
surface.  You should consult magazine articles for details, as it
is too complex to reproduce here.  RLL generally writes more
"net" data than MFM methods.  It also requires a special
controller and a certified RLL disk (at least for reliable
operation, see numerous other postings on this group about using
non-RLL surfaces).  

There is also ARRL, which is even more efficient than RLL.
There are probably others as well.