SUMMARY: Serial line speed for modem

From: J. Chris Hanson (
Date: Wed Jan 19 1994 - 05:01:44 CST

Hello again Sun Managers!

Thanks again for all of your quick responses. Here is a copy of my
original post:

> I have just upgraded our sites modem to a US Robotics 14.4 KBaud modem. We
> are able to run at 14.4 w/ V42bis compression. This should give us a pretty
> decent throughput. My question is this: What speed should I be running my
> serial connection to the Sun at? We are currently running at 19.2 Kbaud, but
> one of my hardware engineers said that he didn't think this would be fast
> enough to handle this speed (especially with compression enabled).

The answer is: Definitely increase the speed of the serial lines!

Apparently, the compression can be (theoretically) as much as 4:1 giving
a throughput of up to 56k! The answers vary on how fast the Sun's serial
lines can be run, but I have bumped it from 19.2 to 38.4 and it seems to
be running fine. There are plenty of aftermarket SBus cards that allow
faster speeds, but I was told that 38.4 is fine for the vast majority of

The only point nobody seems to be clear on is this: Many respondents
claim that the hardware flow control on the Sun serial ports doesn't
work. Therefore if the modem is blasting the computer data, you could
loose some. If this is true, it is also pointed out that the third
party vendors who make SBus serial boards, use flow control and don't
have this problem.

I will continue to use the Sun ports and will follow up on this summary
if any further information/developments occur.

Thanks to all who responded. I would include a list, but it was much
to long to try to repeat accurately. Thanks again!


Chris Hanson

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