Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.protocols.appletalk
Subject: Re: Enhanced LocalTalk (was: Mac Booster Modules)
Message-ID: <9241@hoptoad.uucp>
Date: 10 Dec 89 07:33:52 GMT
References: <6662@imag.imag.fr> <24772@cup.portal.com>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 47

bordier@imag.imag.fr (Jerome Bordier) writes:
>>In November BYTE (p.219), Tom Thompson states that "the faster
>>DaynaTALK and FlashBox modules can coexist with devices running at the
>>slower, standard LocalTalk transfer rate, such as Macs without
>>enhanced connectors, laserprinters, and certain network bridges." Is
>>it true inside one LocalTalk zone ? (my local distributor told me that
>>any Mac in one zone must have the booster module).
 
Yes, it is true, at least of FlashTalk.  FlashTalk Macs can coexist
with LocalTalk Macs.  I don't know about DaynaTalk.  Your distributor
done you wrong.

In article <24772@cup.portal.com> MacUserLabs@cup.portal.com (Stephan
- Somogyi) writes:
>The quick answer to your question is that non-Mac LocalTalk devices
>can't be used at enhanced LocalTalk speeds, unless they specificically
>support enhanced LocalTalk. I can't think of anything out there that
>does this. StarControllers will work, but that's about it (as far as I
>can remember).
 
Obviously, non-upgraded Macs can't use the higher speeds.

>Non-enhanced nodes usually can't see when enhanced nodes are
>transmitting, and will therefore step all over enhanced traffic. This,
>obviously, messes things up a bit.

A rather vague and misleading phrase.  Yes, LocalTalk Macs will step on
FlashTalk packets, requiring retransmission.  However, this does not
cause any serious problems, other than some performance degradation.

The real issue with these acceleration products is that they simply
don't deliver much extra performance.  Even between two accelerated
Macs on the same network, you'll be lucky to get 1.5 speedup, much less
the three times one would expect from a naive application of the
network bandwidth improvement.  Network protocol performance is
generally bounded far more by per-packet overhead on the interpreting
machines than by the raw bandwidth on the network.  If there's an
enormous difference -- for instance, the factor of roughly 30 between
LocalTalk and EtherNet -- then you will see much better performance on
the faster network, but when the differences are small, such as the
factor of 3 between LocalTalk and either FlashTalk or DaynaTalk, the
per-packet overhead will continue to predominate and any actually
performance improvements will be nearly indetectable.
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com

"God must be a Boogie Man." -- Joni Mitchell