Re: [Discuss-gnuradio] Large RX Delay

[Thomas Schmid]

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
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.

Thomas

On 11/13/06, Daniel O'Connor <address@hidden> wrote:
> On Tuesday 14 November 2006 11:33, Thomas Schmid wrote:
> > First of all, I don't understand why we have such a high delay.
> > Shouldn't it be more in the hundreds of /mu s instead of in the ms
> > range? Second, why is the delay shorter for decimation 64, and again
> > larger for a decimation of 256?
>
> How many times a second is your OS switching process context?
> How are you frobbing the parallel port? Does it involve a syscall?
>
> --
> 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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