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From: mhw@fithp (Marc Weinstein)
Newsgroups: comp.sys.3b1
Subject: Re: more on the HFC saga
Message-ID: <1991May22.041659.13189@fithp>
Date: 22 May 91 04:16:59 GMT
References: <102086@becker.UUCP>
Distribution: na
Organization: Weinstein Consulting
Lines: 42

From article <102086@becker.UUCP>, by bdb@becker.UUCP (Bruce D. Becker):
> In article <1991May18.140028.11062@highspl> burris@highspl (David Burris) writes:
> |Does anyone have the source code for the existing drivers? Also,
> |does the HARDWARE support HFC on input? Or more simply, are both the
> |RTS & CTS lines connected to the RS-232 and the UART?
> 
> 	I'm puzzled about your belief that HFC is
> 	a requirement for 19200 bps connections.
> 	This is certainly not the case as far as
> 	I can see.

Lucky you.

>       I've been using 19200 bps
> 	successfully for a long time without
> 	ever using HFC, as have many others.

Sending??  Receiving??  Idle system or lots of activity???

There are many factors here.  If you have very compressible data, and
your port rate is set to 19200 and you are using MNP5 or V.42bis, you
will see transfer rates getting close to 1900 Bps.  The UNIXPC can barely
pump out data that fast, let alone receive it.  However, if you are using
the 'g' protocol in UUCP, or XMODEM (anything which sends blocks of data
with ACKs in between), then you don't start to really push things.

Try using MNP5 plus the UUCP 'e' protocol, and start up two compiles
in the background.  If you can't make it croak, you are indeed lucky.

I'm beginning to think that there *ARE* select PCs out there which may
just be able to handle these higher throughputs.  I know of at least
one 3b1 which can communicate with a Sun using V.42bis, 19200 port rate,
and sees ~1800 Bps with no data corruption.  Mine can't do this, and I'm
not sure what the difference is.  Perhaps the port rate is not exactly
19200 on some systems - perhaps the CPU clock is just a bit faster.

Anyone care to speculate?

-- 
Marc Weinstein
{simon,royko,tellab5}!linac!fithp!mhw		Elmhurst, IL
-or- {internet host}!linac.fnal.gov!fithp!mhw