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PA2AGA > PACDIG 03.03.99 03:11l 136 Lines 5396 Bytes #-9939 (0) @ EU
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From: pa2aga
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Subject: PacketRadioDigest 99/47C
X-BBS-Msg-Type: B
days when a PC ran at 4.77 MHz, it did serve a useful purpose.
But that day is long gone. It now serves as a bottleneck.
>It is one of the few devices in amateur
>radio that has a CPU.
I suppose the CPUs in our radios don't count. :-)
> The only reason I think you might want to use one would be cost.
>Used PC's are so cheap and capable that you could turn them into a TNC
>with a BayCom modem.
You could, and it would likely be better than using the PC as a dumb
terminal to an external TNC. But the simple Baycom modem isn't
a very good modem. It'll suffice for strong signals at low speeds, but
it won't do for weak signals (there, host based DSP and a sound card
is better), and it won't do for higher speed signals (there, a RF modem
and a DMA HDLC card plugged into the host bus and providing interrupt
per frame work better).
Virtually the only time you'd want to use a TNC is if all you have is a
dumb terminal to talk to it. In nearly every other case, you'll be better
off using something with a tighter coupling to the host so that you
can exploit the host's power, and the intimate connection to the channel,
to more efficiently accomplish the communications task.
To equal those advantages with a TNC, the TNC would need to have
the speed and memory of at least a low end PC, so that it can handle
the entire protocol stack as a router, and have an ethernet interface to
your host machine. But as has been pointed out, PCs are cheaper than
dedicated hardware routers, so it makes sense to just use the PC
in the first place, eliminating the bottleneck and expense of the TNC.
Gary
Gary Coffman KE4ZV | You make it |mail to ke4zv@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
>.
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Date: Mon, 1 Mar 1999 19:28:54 GMT
From: nomail@pe1chl.demon.nl (Rob Janssen)
Subject: Why a TNC?
Robin Gilks <g8ecj@gb7ipd.freeserve.co.uk> wrote:
>PS. Do you know of a SCC card that works reliably with up-market
>Pentium motherboards? The PA0HZP ones I've used seem to insist
>on the the extra I/O delays compiled under Linux.
The I/O delays are required for the Z8530. Use a Z85230 and you
won't need them. I don't think it is easily possible to fix it on
the card, Baycom has tried this on the USCC but stretched the wrong
timing.
Rob
--
+----------------------------------+--------------------------------------+
| Rob Janssen pe1chl@amsat.org | WWWhome: http://www.pe1chl.demon.nl/ |
| AMPRnet: rob@pe1chl.ampr.org | AX.25 BBS: PE1CHL@PI8WNO.#UTR.NLD.EU |
+----------------------------------+--------------------------------------+
>.
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Date: Fri, 26 Feb 1999 22:46:52 +0100
From: anders.lageras@usa.net (Anders Lageras)
Subject: Why a TNC?
Rob Kling <rkling@home.com> wrote:
> Thats like saying that embedded systems are useless because the
> technology has been around for 20 years. TCP/IP has been around that
> long too, so have modems. I wonder what he would call the bios on his
> CPU. The TNC is a very efficient device and its fundamental design is
> alive in all sorts of new technology. Moreover, it fits into the
> client/server model very well. It is one of the few devices in amateur
> radio that has a CPU. I think this guy is selling the BayCom type
> modems. The only reason I think you might want to use one would be cost.
> Used PC's are so cheap and capable that you could turn them into a TNC
> with a BayCom modem.
A few years ago when the computers was not as good as to day was tncs
needed. A computer could not handle a packet driver better or as good as
the one a tnc could handle.
But to day are the computers used for packet faster, they can handle a
packet driver much better than the packet driver a ordinary tnc can
handle. The cpu of a tnc is to slow for the packet drivers of today.
There excists tncs with faster cpus, but they are for high speeds mainly
tnc3 and tnc4 for example.
This makes a ordinary tnc much less good working than a computer with a
good apcket driver and a cheap modem. This is solved by the use of kiss
or 6pack, when kiss is used doesn't it work very good at al.
But to buy a tnc for this purpose is stupid.
To day are there no need for tncs for speeds under 38k4, there are many
different good hardwaresthat is cheaper and better.
Like yam, different scc cards, the baycom modems etc.
So the situatioin is differrent to day.
The here are very few people who really need a low speed tnc.
Also for pc based nodes bbses etc are tncs history!
To use a old 386 or 486 computer for then packet driver and maybe a node
will work much better than any tncs. The can the comptuer be connected to
the bbs computer via a serial link etc.
--
73 de SM7UZI Anders Lagerås
>.
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End of Packet-Radio Digest V99 #47
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