Newsgroups: comp.sys.mac.hardware
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!bronze!tagreen
From: tagreen@bronze.ucs.indiana.edu (Todd A. Green)
Subject: Re: Mac+ terminal emulation speeds
Message-ID: <1991Mar25.143425.15057@bronze.ucs.indiana.edu>
Organization: Indiana University, Bloomington
References: <1991Mar22.155813.11505@rcf.rsmas.miami.edu>
Date: Mon, 25 Mar 91 14:34:25 GMT
Lines: 63

In article <1991Mar22.155813.11505@rcf.rsmas.miami.edu> miller@rcf.rsmas.miami.edu writes:
>As a followup to the Mac+ accelerator thread, I posted an article regarding
>the speed of terminal emulators (e.g., Versaterm Pro) and whether or not they
>would run faster on an accelerated Mac+. I stated that my Mac+ running
>Versaterm was much slower than a "real" terminal connected to the same line.
>After further (more careful) comparisons, I see that this is not true.

Let's think of where the bottle necks are occuring here.  Is it the
speed of the CPU, or is it your modem, or is it how fast your machine
can write to the screen or is it a combination of the 3 (or are there
other factors).  I can say (rather safely) that the speed of your
modem is the deciding factor and that the speed of your CPU has very
little to do with it, and the screen comes in the middle somewhere.
(Try chaning your bit depth from 1 to 24 and watch the difference ).

>I have listed a file containing 500 80-character lines from a mainframe to the
>Mac+'s screen and to a couple of terminals. Herewith is the data:
>TERMINAL                                       CHARACTERS/SECOND
>DEC VT240                                            460
>Human Designs HDS3200                                889
>MAC+ with Versaterm emulating a DEC VT220            615

Yes but what you do not state is the connection speeds between the
various terminals.  I'll assume they are all the same for a fair
comparison.

>So, there are two surprises here. First, the Mac+/Versaterm VT220 is *faster*
>than DEC's VT240 which is only about half as fast as a third party terminal.
>Second, all 3 are much slower than I would have guessed....
>
>How many characters per second should my nominal 19.2k baud connection yield???

Don't forget that you are NOT at 19.2K "baud" but rather 19.2K bps.
(bits per second).  There is a big difference. You're modem is running
at 2,400 baud carrying 4 bits per signal (Most likely :) ) = 9,600
bps.  Using compression such as MNP-5 you get throughput of 19.2K
using 2:1 compression.  V42.bis gives you 4:1 compression thus
allowing throughput of 38.4k.  Now, you must convert bps to characters
per second.  You cannot just divide by bps/8 to get cps (characters
per second) You must realize that besides sending the data bits you
also have the parity and stop bits. (Which add up to 10 on my
configuration.) So, if you take the cps that you got 615 X 10 = 6150
bps. When I use my Hayes UltraSmartmodem 9600 to connect to IU's NEC
9631's (which are only MNP5 and not v.42 :( ) I usually get throughput
of 924-980 cps.  I've not taken the time to tweak my registers, so it
could possibly get better.  When I call Hayes 1-800 number I usually
get throughput of 22-30K. Gotta love v42!!

Hope this helps....if there are any errors forgive me I've only had 3
hours of sleep...

> [junk deleted]

Todd
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Todd A. Green   "<_CyberWolf_>"  ---> Pascal <- tagreen@ucs.indiana.edu
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