Questions and answers on MobyTurbo(Tm)


Q: Does MobyTurbo disable or reduce error correction?
A: MobyTurbo does not disable or reduce ZMODEM's error correction
capability.  MobyTurbo uses 32 bit CRC and the same ZMODEM logic as
regular ZMODEM transfers.

Q: Does MobyTurbo require an error correcting modem?
A: No. ZMODEM with MobyTurbo works with regular modems even when
the phone lines are As Nasty as they Want to Be. (sorry)

Q: What problems might occur if DSZ incorrectly identifies a suitable path?
A: If MobyTurbo is used over a path that is not sufficiently transparent,
the transfer will fail at the same point whenever a particular file
is attempted.  MobyTurbo will work over any path that supports YMODEM-g.
MobyTurbo will work over any path that supports XMODEM-1k that does not
suffer from flow control problems.


Q: Why is MobyTurbo just for compressed files?
A: MobyTurbo will transfer any type of file.  Moby Turbo is a performance
enhancement added in response to feedback about YMODEM-g being faster on
compressed files than ZMODEM.  MobyTurbo is optimized for compressed
files.  Other types of files may transfer faster with ZMODEM compression
(sz -Z) depending on their data patterns.




As for the word MOBY: (from JARGON.TXT)

MOBY [seems to have been in use among model railroad fans years ago.
   Entered the world of AI with the Fabritek 256K moby memory of
   MIT-AI.  Derived from Melville's "Moby Dick" (some say from "Moby
   Pickle").] 1. adj. Large, immense, or complex.  "A moby frob."  2.
   n. The maximum address space of a machine, hence 3. n. 256K words,
   the size of a PDP-10 moby.  (The maximum address space means the
   maximum normally addressable space, as opposed to the amount of
   physical memory a machine can have.  Thus the MIT PDP-10s each have
   two mobies, usually referred to as the "low moby" (0-777777) and
   "high moby" (1000000-1777777), or as "moby 0" and "moby 1".  MIT-AI
   has four mobies of address space: moby 2 is the PDP-6 memory, and
   moby 3 the PDP-11 interface.)  In this sense "moby" is often used
   as a generic unit of either address space (18. bits' worth) or of
   memory (about a megabyte, or 9/8 megabyte (if one accounts for
   difference between 32.- and 36.-bit words), or 5/4 megacharacters).
   4. A title of address (never of third-person reference), usually
   used to show admiration, respect, and/or friendliness to a
   competent hacker.  "So, moby Knight, how's the CONS machine doing?"
   5. adj. In backgammon, doubles on the dice, as in "moby sixes",
   "moby ones", etc.
   MOBY FOO, MOBY WIN, MOBY LOSS: standard emphatic forms.
   FOBY MOO: a spoonerism due to Greenblatt.

The following is the best summation of MobyTurbo I've seen yet:

From:     Chuck Miller 
Opus:TB Area:62 D/L:Fri Feb 23 04:16:55 1990
To:      Eric McKinney                            Msg #54, 19-Feb-90 03:02pm
Subject: Re: YMODEM

Eric, the new MobyTurbo option to ZMODEM-90 is really nice.  I have been using
it for some weeks now and am very impressed.  
  
The way it works is that standard ZMODEM is completely network compatible,
meaning that it protects special control characters which packet switching
networks either lose or use or grab etc. for their own use and screw up many
types of protocol transfers.  What this protection means in effect is that
ZMODEM must examine each and every byte of data it processes, compare it to a
list of special characters, take appropriate action if necessary, then send
the byte.  This action obviously takes up a significant amount of overhead,
almost 5% I think.
  
What Forsberg did with MobyTurbo was to make it an option to eliminate this
network protection for those users (most of us) who don't need it all of the
time, and just send the file with all of the usual ZMODEM stuff except the
network protection.  This makes for significant increases in transfer speed. 
I used to get 228-232 cps for non-MNP ZMODEM transfers without MobyTurbo, I
now routinely get 237-239 cps non-MNP with MobyTurbo.  
 
There are a couple of gotcha's though.  You can't use MobyTurbo on most
packet-switched networks, and with some types of software only flow control. 
This means that the user needs to test his system out under these conditions
if he feels there might be a problem.  The second gotcha is that the new
ZMODEM-90 extentions of which MobyTurbo is an example, are not going to be in
the public domain.  This means Registered DSZ/ZCOMM or Pro-YAM only need
apply.  Do not bother to get MobyTurbo with Telix et. al.  
  
The new MobyTurbo is reported to be within 0.5% of Ymoden-g speed, but has
FULL ZMODEM 32 Bit CRC error correction, plus all of the usual features such
as error recovery, batch mode, automatic pathnames etc.  
I would think that the fact that MobyTurbo is fully automatic, and nothing
must be done on the recievers end other than allow the file to be sent would
make up for the small differences between MobyTurbo and Ymodem-g.  I recently
sent a file of approx 100 Kbytes length over 2400 bps non-MNP using both
MobyTurbo and Ymodem-g, and got approximately 2 seconds difference in total
transfer time.  The rub is that with my poor error prone typing ability, I
probably wasted much more than 2 seconds on my end setting up the Ymodem-g
receive, while with MobyTurbo I did nothing but sit back and let Pro-YAM get
the file.  From my perspective this makes MobyTurbo indeed faster than
Ymodem-g, unless you are a very fast and very accurate typist.  Nuff said?
 
Chuck Miller **** Timestamped: 1606:58 02-19-90  
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