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From: japplega@csm9a.UUCP
Newsgroups: comp.os.minix
Subject: Re: "Brooklyn Bridge" (115Kb serial i/o), slave cards, etc.
Message-ID: <467@csm9a.UUCP>
Date: Tue, 7-Jul-87 00:37:38 EDT
Article-I.D.: csm9a.467
Posted: Tue Jul  7 00:37:38 1987
Date-Received: Sat, 11-Jul-87 16:09:17 EDT
References: <227@amanue.UUCP>
Organization: Colorado School of Mines
Lines: 21

I know the people who wrote the original LapLink (and are currently sueing
Traveling Software over the trademark) and a few weeks ago they showed me the
code.... it's amazingly simple to get 115,000 baud.... they directly write
to the 8250 and set a divisor latch at 1 and the hardware does the rest!
The real trick is the routine to write to the 8250... it is a pointer to
a byte of the file being transfered (which their Turbo Pascal program already
moved into heap space)... they output a byte the inc the pointer... it only
takes 8 cycles... oh yes they check the pointer against the end of the file...
and they counted the number of bytes when they loaded it... I don't think
it's practical for networking.... it requires all the CPU can give!!! and then
every packet would have to be preloaded into a memory location prior to sending


    Joe Applegate - Colorado School of Mines Computing Center
            {seismo, hplabs}!hao!isis!csm9a!japplega
                              or
 SYSOP @ M.O.M. AI BBS - (303) 273-3989 - 300/1200/2400 8-N-1 24 hrs.

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