Lars Segerlund wrote: > Ok, I will check how the latency in device drivers are, perhaps they > are not so bad, atleast for x86 , I was thinking arm .... someone was > mentioning they had to do some copying on interrupts ( ie, context > switches ... ). > Lets investigate, it's no worse than a scope to the parport and > setting one pin with outb and another with a driver. > I've already done this in user mode on the Beagle Board. You can't change the state of a GPIO pin faster than 240 ns. Apparently the GPIO hardware is multiplexed, and the hardware scans each GPIO bank every 240 ns. It appears the CPU goes into a wait state until the GPIO performs the action requested. Somebody on the Beagle list claims a device driver is much faster, but I have doubts he measured it right.
On x86 hardware, motherboard parports are pretty slow, so you can't flip a parport bit much faster than 500 ns or so. But, it would be fine for testing interrupt latency and jitter. Jon ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
