Date: Fri, 03 Oct 1997 22:46:13 -0700 From: "Michael L. VanLoon -- HeadCandy.com" <michaelv@MindBender.serv.net> To: "John T. Farmer" <jfarmer@sabre.goldsword.com> Cc: gurney_j@resnet.uoregon.edu, freebsd-hardware@freebsd.org, jfarmer@goldsword.com Subject: Re: Multiple serial ports Message-ID: <199710040546.WAA00758@MindBender.serv.net> In-Reply-To: Your message of Fri, 03 Oct 97 21:16:22 -0400. <199710040116.VAA07559@sabre.goldsword.com>
next in thread | previous in thread | raw e-mail | index | archive | help
>
>On Thu, 2 Oct 1997 18:54:13 -0700 John-Mark Gurney said:
>>John T. Farmer scribbled this message on Oct 2:
>>> Uh, actually, I've had good success with with several different brands
>>> for multiple terminals/printers/front-end system consoles all active at
>>> the same time. Granted, I don't try to run the ports at greater than
>>> 56kbps. Frankly, you don't need to.
>>why exactly?? a friend was dialed into my machine (using a 14.4k
>>internal!!) and we were sending some text down the line.. and he was
>>able to get 8kbytes/sec+ over the link.. and this is with a zoom 14.4k,
>>and a zoom 28.8k modem... if I wasn't running the zoom at 115.2kbps, we
>>wouldn't of been able to do that... and instead would of slowed a
>>14.4kbps call... (think if it was a 28.8k??)
>
> Ah, increasing the line speed does not necessarily mean that
> latency will go down. The latency of a 32k synchronous digital
> link (FR connection, for example) is usually less than the
> latency of a 33.6k analog modem connection. A lot of the
> latency reduction in your example is due to difference between
> 14.4 & 28.8 modems. Modem brnad will also play a factor, not
> to mention the effect of flow control on each leg...
However, this doesn't disprove the fact that you need to run your
ports much faster than 56Kbps if you expect to get any compression at
all out of your 33.6-56K modem.
Remember, the ports need to run as fast as the _uncompressed_ data,
going in and/or coming out, or else compression is going to do nothing
for you but add latency.
I. e. if you want to be able to stream data through a 28.8K modem,
with full 4x compression, you need to be running your serial ports at
least as fast as 4x28.8K, or 113.2Kbps. Granted, there isn't very
much out there except plain text that is this compressible. But, 2x
isn't hard to do with generic network traffic, and one of the most
popular things to do right now (surf the web) is comprised of large
amounts of plain text (combined with alread-compressed graphics, of
course). The graphics will come over mostly at native modem speed,
since they're already compressed. But your text won't come over any
faster if you don't run your serial ports faster.
-----------------------------------------------------------------------------
Michael L. VanLoon michaelv@MindBender.serv.net
Contract software development for Windows NT, Windows 95 and Unix.
Windows NT and Unix server development in C++ and C.
--< Free your mind and your machine -- NetBSD free un*x >--
NetBSD working ports: 386+PC, Mac 68k, Amiga, Atari 68k, HP300, Sun3,
Sun4/4c/4m, DEC MIPS, DEC Alpha, PC532, VAX, MVME68k, arm32...
NetBSD ports in progress: PICA, others...
-----------------------------------------------------------------------------
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199710040546.WAA00758>