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[ts-7000] Re: rtc7800 vs. hwclock

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Subject: [ts-7000] Re: rtc7800 vs. hwclock
From: "charliem_1216" <>
Date: Fri, 06 Feb 2009 05:23:12 -0000
Hi Dan --

--- In  "Dan" <> wrote:
>
> I've got a ts7800 board with the RTC option.  Both hwclock and rtc7800
> exist on my installation seem to work correctly as far as I can tell.  
> 
> - What is the difference between the two?  From what I gather hwclock
> is part of a standard linux distribution that uses an rtc driver to
> access the clock and rtc7800 just goes to the clock directly.

If the linux kernel rtc driver is looking at the same hardware as the
rtc7800, then they should behave the same.

> 
> - Why would I want to use one vs. the other?

Well, hwclock is more portable among different linux systems &
architectures.  Maybe you have both TS ep9302 and ts-7800 boards and
want to keep the same source.  Also, FWIW, the kernel can have more
than one RTC now, if you have the hardware.  The ep9302 boards have a
 rather useless (non-battery backed) RTC on the chip, as well the
(optional) RTC chip.

> - If I need to get the date/time in one of my programs, why do I want
> to use the system time instead of the hardware clock time?

I'd definitely use posix system time stuff: it's more portable, knows
about your TZ & DST, it's trimmed by your NTP server, etc.  IIRC,
getting time from the hardware can have significant delays, and may be
in UTC depending on who set up the board.

regards, ....... Charlie

> Thanks,
> Dan
>




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