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 GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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