* [Xenomai-help] rtcan and USB legacy
@ 2007-08-18 11:59 Roland Tollenaar
2007-08-18 15:35 ` Gilles Chanteperdrix
0 siblings, 1 reply; 3+ messages in thread
From: Roland Tollenaar @ 2007-08-18 11:59 UTC (permalink / raw)
To: Xenomai-help
Hi,
I have understood that USB legacy set to be on in the BIOS is a
potential cause for latency issues. Is that correct?
I have it turned on due to the fact that I boot from USB. I'd like to
know how severe the problems might be. Does anyone have experience with
this?
Regards,
Roland.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Xenomai-help] rtcan and USB legacy
2007-08-18 11:59 [Xenomai-help] rtcan and USB legacy Roland Tollenaar
@ 2007-08-18 15:35 ` Gilles Chanteperdrix
2007-08-18 15:58 ` Roland Tollenaar
0 siblings, 1 reply; 3+ messages in thread
From: Gilles Chanteperdrix @ 2007-08-18 15:35 UTC (permalink / raw)
To: rolandtollenaar; +Cc: Xenomai-help
Roland Tollenaar wrote:
> Hi,
>
> I have understood that USB legacy set to be on in the BIOS is a
> potential cause for latency issues. Is that correct?
>
> I have it turned on due to the fact that I boot from USB. I'd like to
> know how severe the problems might be. Does anyone have experience with
> this?
I guess the answer depends on the BIOS implementation of the legacy
emulation. I suppose you can observe latencies around some tens of
microseconds.
That said:
- I really doubt that you need legacy USB emulation to boot from USB;
- in some cases, loading the Linux USB HCIs drivers is known to turn off
the legacy USB emulation.
--
Gilles Chanteperdrix.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Xenomai-help] rtcan and USB legacy
2007-08-18 15:35 ` Gilles Chanteperdrix
@ 2007-08-18 15:58 ` Roland Tollenaar
0 siblings, 0 replies; 3+ messages in thread
From: Roland Tollenaar @ 2007-08-18 15:58 UTC (permalink / raw)
To: Gilles Chanteperdrix; +Cc: Xenomai-help
> > I have it turned on due to the fact that I boot from USB. I'd like to
> > know how severe the problems might be. Does anyone have experience with
> > this?
>
> That said:
> - I really doubt that you need legacy USB emulation to boot from USB;
Why do you say this? I strongly had the impression that I needed to turn
it on to get the system to boot from USB but turned it on together with
another innocuous option. Maybe the innocuous option was not so innocuous?
> - in some cases, loading the Linux USB HCIs drivers is known to turn off
> the legacy USB emulation.
This may be the case on this machine. I don't notice any detrimental effect.
Roland
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2007-08-18 11:59 [Xenomai-help] rtcan and USB legacy Roland Tollenaar
2007-08-18 15:35 ` Gilles Chanteperdrix
2007-08-18 15:58 ` Roland Tollenaar
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