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Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!hellgate.utah.edu!helios.ee.lbl.gov!nosc!humu!pegasus!richard
From: richard@pegasus.uucp (Richard Foulk)
Newsgroups: comp.unix.xenix,comp.unix.i386
Subject: Re: Equinox multi port boards
Message-ID: <1989Dec12.180940.24190@pegasus.uucp>
Date: 12 Dec 89 18:09:40 GMT
References: <458@gallium.UUCP> <134@tiamat.fsc.com> <3323@qiclab.UUCP> <1095@crpmks.UUCP>
Reply-To: richard@pegasus.UUCP (Richard Foulk)
Organization: Pegasus
Lines: 33

>>[..]                                   In the meantime, what I remember them
>>saying is that the board will do 38.4K output on 24 ports, no problem.  I don't
>>about input, and I'm embarassed to say I never even thought of asking (although
>>I expect the output to input ratio to be 20:1 or more).  
>>>>>>>>>>>>>>>>>>>>>>>>>>
>
>It's more like 1:1.  The ASIC provides baudrate processing of 38.4K x 24 
>channels on output, 38.4K x 24 on input, and a total aggregate baudrate for 
>both input and output processing at 38.4K x 48.  In other words, the processor 
>handles these baudrates on all 24 channels for both input and output 
>simultaneously and with very little cpu overhead because no extra interrupt 
>servicing is required.  It's going to be tough to beat that with a stick, let 
>alone with some of the other serial boards and drivers out there.
>   

That seems mighty optimistic, at least in the real world.  Sure the board
may be able to pump data at some wonderful rate in some ideal situation,
but real world applications aren't that cooperative.

Output with Unix is usually no problem -- high performance is relatively easy.
Input with Unix is just the opposite.

So how do these boards perform in the real world, handling real tasks.  How
do they compare to their competition?

Unix I/O is the sort of thing that you can easily throw all kinds of
expensive hardware at and not gain a whole lot.  Or employ some careful
tuning and make all the difference in the world.

-- 
Richard Foulk		richard@pegasus.uucp
			richard%pegasus.uucp@nosc.mil
			richard@uhccux.uhcc.hawaii.edu