[time-nuts] clock-block any need ?

Attila Kinali attila at kinali.ch
Thu Dec 27 19:48:43 UTC 2012

On Thu, 27 Dec 2012 11:30:37 -0800
Jim Lux <jimlux at earthlink.net> wrote:

> So, what about the USB-Ethernet dongles?  (I use them a lot at work to 
> add a second interface for a laptop in test equipment setups, talking to 
> a Prologix, for instance)

A lot worse! One thing is that USB has a polled protocol (ie the host
has to ask whether the device has any data) and the slot when an USB
device can signal that a packet came in repeates it self at most a couple
of times per 1ms frame for FS (don't know from the top of my head for HS).
The bigger issue though is that drivers for ethernet dongles are usally
of quite bad quality (ie it takes them a long time to do anything), and
they try to queue as much as possible to increase troughput (which adds
unpredictable delay).

			Attila Kinali
There is no secret ingredient
         -- Po, Kung Fu Panda

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