On Fri, 15 Jul 2005, Paul Jakma wrote: > On Thu, 14 Jul 2005, Christoph Lameter wrote: > > > Linux can already provide a response time within < 3 usecs from user space > > using f.e. the Altix RTC driver which can generate an interrupt that then > > sends a signal to an application. The Altix RTC clock is supported via POSIX > > timer syscalls and can be accessed using CLOCK_SGI_CYCLE. This has been > > available in Linux since last fall and events can be specified with 50 > > nanoseconds accurary. > > Out of curiosity, are there any cheap and 'embeddable' linux supported > architectures which support such response times (User or kernel space)?
Well, just implement the proper hooks for the HPET so that you can use CLOCK_HPET from user space. > Input comes in at anywhere from 6kHz to 100kHz (variable), (T0 say), > requirement is to assert an output line Ta seconds after each T0, Ta needs to > be accurate to about 6us in the extreme case (how long the output is held has > similar accuracy requirement). Well the interrupt latency depends on many things in the linux kernel. Worst case is much greater than 6us. You probably need the RT patches as well. > What kind of hardware is capable of this? Even in microcontroller space it's > difficult to do (eg looked at some ARM microcontrollers, which still have > several usec of interrupt latency - even with no OS, still likely cant use > timers and interrupts.). Try HPET which is pretty standard these days. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
