I found this: http://rt.wiki.kernel.org/index.php/RT_PREEMPT_HOWTO#Configuration_and_Compilation
quote: activated the High-Resolution-Timer Option (Attention, the amount of supported platforms by the HR timer is still very limited. Right now the option is only supported on x86 systems, PowerPC and ARM Support are however in queue.) disabled all Power Management Options like ACPI or APM (not all ACPI functions are "bad", but you will have to check very carefully to find out which function will affect your real time system. Thus it's better to simply disable them all if you don't need them. APM, however, is a no-go.) NOTE: Since rt patch 2.6.18-rt6 you will probably have to activate ACPI option to activate high resolution timer. Since the TSC timer on PC platforms, as used in the previous versions, are now marked as unsuitable for hrt mode due to many lacks of functionalities and reliabilties, you will need i.E. pm_timer as provided by ACPI to use as clock source. To activate the pm_timer, you can just activate the ACPI_SUPPORT in menuconfig and deactivate all other sub modules like "fan", "processor" or "button". If you have an old pc, which lacks ACPI support, you migh have problems using the high resolution timer. endquote If I understand that well, we have to enable ACPI on recent kernel on x86. If I look at the kernel config for the 2.6.21, it is a Power Management Timer Support (CONFIG_X86_PM_TIMER) that also must be enabled. Another question. Have somebody already try to do a thickless system? Processor Type and Features -> Tickless System (NO_HZ) What I don't understand is at when I select it, I still have the Timer Frequency (Hz=1000) option. Or maybe at I don't understand what it is... Ciao, Dominique
