Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!unido!mpirbn!p554mve
From: p554mve@mpirbn.mpifr-bonn.mpg.de (Michael van Elst)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: second serial port
Keywords: 2232 7 port
Message-ID: <1409@mpirbn.mpifr-bonn.mpg.de>
Date: 4 Dec 90 19:25:05 GMT
References: <14383@crdgw1.crd.ge.com> <90334.151404DXB132@psuvm.psu.edu> <1990Dec2.141048.10108@NCoast.ORG> <1990Dec3.053356.26826@monu6.cc.monash.edu.au>
Reply-To: p554mve@mpirbn.UUCP (Michael van Elst)
Organization: Max-Planck-Institut fuer Radioastronomie, Bonn
Lines: 34

In article <1990Dec3.053356.26826@monu6.cc.monash.edu.au> edp367s@monu6.cc.monash.edu.au (Rik Harris) writes:
>davewt@NCoast.ORG (David Wright) writes:
>>switch box. If you try to run 3 or 4 terminals at 9600 baud without a CPU
>>on the I/O board you will see significant speed loss.
>
>A CPU will add convenience to the design of a piece of hardware, not speed.
>A CPU needs to be clocked, and must access memory, and the hardware is
>limited by the speed the CPU can run at.
>
>from the CPU, because it is too slow.  We have built specialised
>circuits to have the hardware do all the buffering and switching of
>packets without CPU intervention.

It's true that a serial board with a CPU is limited to the speed of
that CPU but your "specialised curcuit" isn't a good comparison, maybe
the term CPU is a little confusing.

What was meant is that with the Amiga, there are two types of serial
boards. One uses plain UARTs while the other uses a dedicated CPU
to control these UARTs. The dedicated CPU makes this solution faster
since the "dumb" board has to be controlled by the main CPU whereas
the dedicated CPU can work in parallel and reduce overhead by buffering
requests.

So the difference is the "intelligence" of the board. This can be achieved
with a CPU or with some hardware with higher sophistication than a plain
UART.

Regards,
-- 
Michael van Elst
UUCP:     universe!local-cluster!milky-way!sol!earth!uunet!unido!mpirbn!p554mve
Internet: p554mve@mpirbn.mpifr-bonn.mpg.de
                                "A potential Snark may lurk in every tree."