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From: williams@umaxc.weeg.uiowa.edu (Kent Williams)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: How to set serial port to 115k baud?
Message-ID: <3835@ns-mx.uiowa.edu>
Date: 9 Jan 91 13:02:32 GMT
References: <1991Jan5.034731.15478@d.cs.okstate.edu> <1839@gold.gvg.tek.com> <3815@ns-mx.uiowa.edu> <9493@scolex.sco.COM>
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In article <9493@scolex.sco.COM> md@sco.COM (Michael Davidson) writes:
>Read what Greg wrote!! (and a 16450 data sheet!) The clock frequency
>in this case is 1.8432Mhz - loading the 16450 divisor latch with a
>value of 1 gives an effective divisor of 16 - that's just the way the
>divisor latch is implemented on the 16450 ....
>

OK, you're right.  I don't know the 16X50 series that well.  With a
Zilog SIO, the value you write to the divisor latch IS the clock
divisor.  Divide by 16 should work great; even divide by 2 works OK.

>You *can* run a 16450 at 115.2K bps but your mileage will certainly
>vary - the 16450 or 16550 will probably hold up OK but you may have
>some problems with with the RS232 drivers - and don't expect to get
>away with more than a few feet of cable at that speed.
>
Even with a 386, 115.2K is pushing the limit of what you can do with
interrupt driven communication.  The queue in the 16550 would help some.
Has anyone at SCO run a dumb card under unix at 57K?


--
             Kent Williams --- williams@umaxc.weeg.uiowa.edu 
"'Is this heaven?' --- 'No, this is Iowa'" - from the movie "Field of Dreams"
"This isn't heaven, ... this is Cleveland" - Harry Allard, in "The Stupids Die"