Re: [Discuss-gnuradio] Large RX Delay

[Daniel O'Connor]

On Tuesday 14 November 2006 12:10, Thomas Schmid wrote:
> I use the outb command to change the parallel port. From what I read,
> that command should have a delay of around 1 \mu s, not more. I am not

Hmm, well you probably will incur a few microseconds because you need to talk 
to the legacy hardware which tends to be very slow.

You won't have any context switch or syscall overhead though.

> sure about the context switches, but I am almost sure that this is not
> the problem. I don't run anything else on the machine (i.e., no other
> heavy load process), and the machine is pretty powerfull (dual CPU,
> dual core with huyper threading, that makes 8 CPU's under linux). If
> it helps, I am running the stock Ubuntu 6.10 kernel (2.6.17-10-generic
> #2 SMP Fri Oct 13 18:45:35 UTC 2006 i686 GNU/Linux). Additionally, I
> was able to measure the TX delay for burst transmission with a similar
> technique to be in the order of a couple of hundred \mu s. This is why
> I am wondering about the large RX delay.

Not sure hyperthreading is a good idea here. The virtual cores may be stalled 
without you really knowing. I wouldn't imagine it would have such a large 
effect as you are seeing though.

Not really sure what else to try though sorry..

-- 
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
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