Hello, I want to use delays of 1 microsend on linux 2.4 or linux 2.6 kernel on x386 platform. As we know, usleep depends on the HZ of the system. So both in 2.4 and in 2.6 we cannot achieve 1 microsec delay calling udelay (the man page of usleep says itslef that "Probably not accurate on many machines down to the microsecond."). According to "Linux I/O port programming mini-HOWTO" (http://www.tldp.org/HOWTO/IO-P ort-Programming-2.html) you can use outb on 0x80 to create a dealy. So I added this snippest of code and trird to use outb('a',0x80) for creating a sleep time in resolution of microseconds thus: ............ ioperm(0x80, 1, 1); for (i=0;i<10000;i++) outb('a',0x80); ............ On 3 machines (each of them had a different strength, one of the with 2.6 kernel and the other two with 2.6 kernek) it gave a result of about 1.4 microsec for every such call, while on a differnet macine it gave a much higher average of 2.16 microsec. That different machine was a strong one, with 3Ghz CPU. >From this results it seems that I cannot rely on this outb() for creating a microsec delay because it gives such different results on different machines. However , the results seems strange : I have 2 almost similiar machines : one gave 2.16 and one gave 1.4 Could it be that something in that machine caused it to do it slower and gicv 2.16 microsec as an average? I must empasize that "top" showed that there did not run something heavy on both these machines.(in terms of cpu and memory) Any idea? John Que -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
