Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!ncar!csn!kessner!chris
From: chris@kessner.denver.co.us (Chris Hanson [Lord Xenon])
Newsgroups: comp.sys.amiga.programmer
Subject: Bizarre Fantasy: RLL Flopies?
Keywords: MFM, RLL, Floppies, Blitter, Clueless, Fantasy, etc.
Message-ID: <1991Apr2.061633.17980@kessner.denver.co.us>
Date: 2 Apr 91 06:16:33 GMT
Sender: chris@kessner.denver.co.us
Organization: The Kessner Institute of Something or Other.
Lines: 39


  Well, gee. Now that I managed to stir up a hornet's nest over in the
Comp.Unix.Amiga section, maybe I'll come over here, and blather on. ;)

  I was scamming the Hardware manual the other day, looking for ways to
improve that audio quality. But that's not what I'm posting about. I noticed
that trackdisk.device uses the blitter to encode data into raw MFM codes,
and back. Now, it's a simple leap of faith to wonder if therefore we
couldn't recode that to utilize the superior RLL 2,7 encoding scheme used
by most (NON-IBM!) hard drives. RLL 2,7 typically gives an approximate
150% storage space increase, presumably by using only 3 bits to encode
2 input bits, instead of MFM's piggish 4 bits out for every 2 bits in.
 
  Now, I know that RLL hard drives use more than just a different type
of encoding algorithm, as you can not always use a MFM HD with and RLL
controller, successfully. Am I missing something? Is anyone out there
familliar with the RLL 2,7 algorithm?

  Technically, by my rough multiplication, this should net us a 1320k
storage capacity on a double-density disk, with standard hardware. Note
that the disk manufacturers rate these double-density disks as having a
maximum capacity of 1 megabyte, UNFORMATTED. It seems to be cheating to
get 1.3 meg out of them. Is it?
 
  This also means that 2640k (2.6 megabytes) could be stored on the 3000T's
150rpm drives. Something to consider.
 
  Am I dreaming? Missing some crucial concept? Clueless? A genius? ;)
 
  Reply, or send me mail. I'll summarize any informational mail I get.
 
   Chris - Xenon

(303)/696-8973 Work, (303)/762-0849 Home, 1-976-DEV-NULL For Flames.
-- 
#define chris Christopher_Eric_Hanson || Lord_Xenon || Kelson_Haldane 
I work, but you don't know who I work for. And I'm not on their machines.
"WYSIKSNCTWYG:What You See Is Kinda Sorta Nearly Close To What You Get." -Me
::I'm chris@kessner.denver.co.us, please.