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From: Willy Tarreau <>
To: Grzegorz Ja?kiewicz <>
Cc: Johannes Stezenbach <>,
	Theodore Tso <>, Joe Barr <>,
	Linux Kernel mailing List <>
Subject: Re: Serial port blues
Date: Sun, 21 Jan 2007 15:58:17 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Sun, Jan 21, 2007 at 03:50:32PM +0100, Grzegorz Ja?kiewicz wrote:
> funny, how even very fast box can be useless for such activities with modern
> kernels, such as linux. After all, serial ports don't require too much
> horsepower to be highly accurate.
> >From designer perspective, I would rather go for uC solution in his case.
> That is, design and build fairly simple board - based on atmega AVRs. 16mhz
> 8bit chip can do so much better compared to N gigs mhz box running "modern"
> operating system, these days....

It is true, but the point is not "modern" vs "ancient" OS, it's "multitasking"
vs "monotasking" kernel. If your program does the busy loop, you'll get a
very high accuracy at the expense of burning watts polling one bit one
billion times a second waiting for a change every millisecond.

18 years ago, I wrote a soft-only 8250 emulator to connect my second 8088
to the first one's serial port at 19200 bauds. At this time, waiting for
a change only took a few hundred cycles and the busy loop was the default
mode of the OS anyway. Things have changed since.


  parent reply	other threads:[~2007-01-21 14:59 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-19 21:37 Joe Barr
2007-01-20 17:36 ` Willy Tarreau
2007-01-21  5:54   ` Theodore Tso
2007-01-21  7:05     ` Willy Tarreau
2007-01-21 14:04       ` Johannes Stezenbach
     [not found]         ` <>
2007-01-21 14:58           ` Willy Tarreau [this message]
     [not found]             ` <>
2007-01-21 18:52               ` Theodore Tso
     [not found]                 ` <>
2007-01-21 19:30                   ` Theodore Tso
2007-01-21 18:55       ` Theodore Tso
2007-01-21  5:09 ` Stuart MacDonald
2007-01-21  7:07 ` H. Peter Anvin
2007-01-21  7:08 ` H. Peter Anvin
2007-01-21 20:44   ` H. Peter Anvin
2007-01-22 11:37 ` Alan

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