Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.os.linux.misc > #11105

Re: Realtime clock accessible without context-switch?

From Clemens Ladisch <clemens@ladisch.de>
Newsgroups comp.os.linux.misc, comp.os.linux.hardware
Subject Re: Realtime clock accessible without context-switch?
Date 2014-05-20 21:56 +0200
Message-ID <bu1qcoFt9amU1@mid.individual.net> (permalink)
References <llfapk$mhc$2@dont-email.me>

Cross-posted to 2 groups.

Show all headers | View raw

Charles T. Smith wrote:
> Is there a way to access (say on Intel platforms) the realtime clock
> without using a special device driver, but simply with non-synchronized
> memory access?

On IBM-PC compatible machines, the RTC lives in the good ol' ISA I/O
space, which cannot be memory-mapped.

When doing ISA I/O accesses, the switch to kernel mode is _not_ the
bottleneck.  If you want to avoid it anyway, use iopl and inb/outb.


Regards,
Clemens

Back to comp.os.linux.misc | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Realtime clock accessible without context-switch? "Charles T. Smith" <cts.private.yahoo@gmail.com> - 2014-05-20 10:29 +0000
  Re: Realtime clock accessible without context-switch? Clemens Ladisch <clemens@ladisch.de> - 2014-05-20 21:56 +0200
    Re: Realtime clock accessible without context-switch? "Charles T. Smith" <cts.private.yahoo@gmail.com> - 2014-05-21 07:29 +0000
      Re: Realtime clock accessible without context-switch? Thomas Richter <thor@math.tu-berlin.de> - 2014-05-21 09:47 +0200
      Re: Realtime clock accessible without context-switch? William Unruh <unruh@invalid.ca> - 2014-05-21 15:51 +0000
      Re: Realtime clock accessible without context-switch? Clemens Ladisch <clemens@ladisch.de> - 2014-05-21 19:32 +0200
        Re: Realtime clock accessible without context-switch? Richard Kettlewell <rjk@greenend.org.uk> - 2014-05-21 23:35 +0100
          Re: Realtime clock accessible without context-switch? "Charles T. Smith" <cts.private.yahoo@gmail.com> - 2014-05-22 07:53 +0000
            Re: Realtime clock accessible without context-switch? Clemens Ladisch <clemens@ladisch.de> - 2014-05-22 20:36 +0200
              Re: Realtime clock accessible without context-switch? Richard Kettlewell <rjk@greenend.org.uk> - 2014-05-22 20:26 +0100
                Re: Realtime clock accessible without context-switch? William Unruh <unruh@invalid.ca> - 2014-05-22 22:48 +0000
        Re: Realtime clock accessible without context-switch? Jan Pieter <jp@jp.dhs.orig> - 2014-06-01 09:58 +0200
  Re: Realtime clock accessible without context-switch? Todd <Todd@invalid.invalid> - 2014-05-23 14:20 -0700

csiph-web