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 <[EMAIL PROTECTED]> 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 GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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