[time-nuts] RPi NTP was Net4501's cheap...

[Herbert Poetzl]

On Sat, May 25, 2013 at 05:06:57PM +0000, lists at lazygranch.com wrote:
> Flightradar24 is using beagle bones in their ADS-B/mode-s
> system and will be incorporating MLAT soon. I suspect they work
> well in timing applications.

> That said, the Allwinner they sell on Sparkfun will probably be
> my next SBC. Though not listed on the wiki, they have opensuse
> running on it.

> BTW, on some linux dists, there is a way to get around the
> clock speed stepping. It may not be universal, but selecting
> "performance" works on opensuse for Arm.

The speed stepping (and similar performance control mechanisms)
are managed by so called 'governors' which are part of the
kernel, and thus do not really depend on the distro.

they can be loaded (as modules) or compiled into the kernel
and they can be controlled via userspace tools or via the
sysfs entries.

HTH,
Herbert

> -----Original Message-----
> From: Paul <tic-toc at bodosom.net>
> Sender: time-nuts-bounces at febo.com
> Date: Sat, 25 May 2013 12:47:38 
> To: <time-nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: [time-nuts] RPi NTP was Net4501's cheap...

> On Sat, May 25, 2013 at 2:43 AM, David J Taylor wrote:

>>  Paul,

>> Just what devices were you hot-plugging to produce this
>> problem? One with an initial current surge outside the USB
>> spec I could understand.

> I was plugging in a USB to RS232 adapter. If you read the
> various bits you'll find about the USB on Rev.B boards
> you'll see all the work-arounds suggested here as well as an
> implication that Raspberry intends to fix the problem in a
> later release.

>> NTP performance on the three Raspberry Pi cards here can be of
>> the same order as FreeBSD running on an Intel Atom PC:

> Yes, I've looked at your stats. As I said earlier you put me
> onto the Pi and the Sure boards. The offsets on the Pi are
> fine. I just don't like the "weak" network performance which
> you can see in the ntpq output for the Pi. Since I'm still
> testing bits all four of my clocks are on the same gigabit
> switch so I don't expect to see simultaneous negative and
> positive offsets. The Laureline is jittery too but at least it
> always presents the same offset "polarity". I'll see how the
> Beaglebones do, check out the next rev. of the Laureline and
> then dither some more.
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