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Subject[OT] high precision hardware (was Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt)
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)?

Would be very interested for a hobby project I'm planning
(programmable digital ignition) which requires about 10usec
resolution +/- 6us accuracy response times. At moment looks like this
task will have to done on a dedicated microcontroller.

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).

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.).

Paul Jakma Key ID: 64A2FF6A
The church saves sinners, but science seeks to stop their manufacture.
-- Elbert Hubbard
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