Path: utzoo!mnetor!uunet!van-bc!sl
From: sl@van-bc.UUCP (pri=-10 Stuart Lynne)
Newsgroups: comp.dcom.modems
Subject: Re: throughput using CTS flow control on a Trailblazer+
Message-ID: <1723@van-bc.UUCP>
Date: 19 Apr 88 10:03:57 GMT
References: <871@spdcc.COM> <1721@van-bc.UUCP> <881@spdcc.COM>
Reply-To: sl@van-bc.UUCP (pri=-10 Stuart Lynne)
Organization: Public Access Network, Vancouver, BC.
Lines: 26

In article <881@spdcc.COM> dyer@spdcc.COM (Steve Dyer) writes:
>If a Trailblazer Plus cannot exploit its own buffering capacity when
>using hardware flow control so as to yield a throughput equivalent to
>the calling party (i.e. 2400 baud incoming to a 19.2kb TB+ should be
>close to 2400 baud throughput), I'd call it a bug.
>
>What do the folks at Telebit have to say?

No, I'd call it a feature.

The TB+ does seem to use it's buffering capacity if you ignore CTS entirely.

By using CTS to throttle the data rate from the host down to 2400 without
buffering things like ^C work well. You interrupt and the host see's it and
stops. With large buffers in the TB+ you can get several more screens of
data. 

With proper hardware support in the host (eg Intel 8274 MPSC) throughput is
bang on 2400 bps because the serial chip responds directly to CTS starting
and stopping output without even telling the host. With a serial chip which
doesn't support CTS directly (eg NS 16450) you get a modem status interrupt
which you have to service.


-- 
{ihnp4!alberta!ubc-vision,uunet}!van-bc!Stuart.Lynne Vancouver,BC,604-937-7532