One thing on the topic of power consumption I'd like to chime in on:
Keep in mind when you slow the processor's HCLK down you must
recalculate the SDRAM refresh rate timing also (since its defined in
terms of number of HCLKs per auto-refresh cycle) Failing to do this
the board will most likely continue running just fine, (due to the
nature of the way minimum refresh rates are spec'ed) but if you put
the board in a hot environment where leakage current is higher, you
may find yourself with a very difficult to trace down memory
corruption bug.
//Jesse Off
--- In Nagaraj Kanniah <> wrote:
>
> Thanks a lot Jim.
>
> I was away for a couple of days, just saw your mail. I would look
into the possible power savings that I can get using your utility.
However, I would like to know if there is any impact if I bring down
the clock rate for sometime (say 2.5 hrs) and then bring it back to
166 MHz for say 0.5 hr. and then bring it down again for 2.5hrs and
so on. Can I cycle the clock rate like this without impact on the CPU
or OS? Is it advisable? Because to save power during the 2.5 hrs
between my data acquisition, I don't need the full speed of the CPU.
Or do I need to reboot?
>
> Thanks and with regards,
> - Nagi
>
> Jim Jackson <> wrote:
>
> On Tue, 20 Dec 2005, nagi_kann wrote:
>
> > Has anyone tried 'Advanced Power Management' on the TS7200?
>
> APM as per the standard APM or ACPI (http://www.acpi.info/) is not
> supported. However there are features you can use to save power.
> You can turn off the Ethernet controller, you can reduce the various
> internal clock rates. I've written a utility (cctl) to assist with
this,
> it's in the software section of my TS7200 web page. Also there are
some
> patches to the kernel to support changing cpu clocking via the cpufreq
> interface.
>
>
> re. ethernet interface, here's what I wrote in a previous thread
on the
> subject..... "I've found that the ether interface can get into a funny
> very slow state if just arbitrarily powered off and on. I would
recommend
> ifconfig'ing eth0 down, and waiting a few secs, before powering
off. And
> on power back up, wait a few secs before ifconfig'ing it up again."
>
> and this is a usefull snippet from Bob Lees from another thread ...
> "Update to clk restriction on enet. Ethernet will work at a
12.5MHz clock
> (CPU and BUS) if the connection is at 10MBit (10baseT) which can
be forced
> by config (haven't done that yet) or by connection to 10MBit hub (have
> done that). In the ep93xx_eth driver the auto-negotiation has been
> disabled (don't know by whom) because it is set in Redboot. This
is fine
> until you start changing the clock or disabling/enabling the phy.
So if
> you intend to change clock and/or disable the phy then you need to
> re-enable the auto-negotiate and then do a ifconfig down, ifconfig up
> around the clock change/enable phy which causes the phy to
re-establish
> proper comms. Not yet clear why the clock change causes the
problem as
> well as the disable/enable, haven't looked at the Micrel data
sheet yet.
> This is NOT in the patch of 250705."
>
> How much power can you save? Well I have an early TS7200 with an
EP9301
> (default CPU clock of 166MHz) and my base line power consumtion is
> 0.35A at 5v (1.75W). Turning the ethernet controller off and
reducing the
> CPU and memory clocks to 20MHz and 10MHz resp. I got power
consumtion down
> to 0.17A at 5V (0.85W).
>
> I'd be interested to see what the savings would be on one of the new
> TS7260 boards - I reckon you could really get the power down,
because the
> residual peripheral board consumption is probably very low.
>
> cheers
> Jim
>
>
> >
> > My application of the TS7200 is a data acquisition system
wherein data
> > acquisition is every 3 hours and the acquisition process takes
just 30
> > to 35 mins. So for roughly 2 hrs, the TS7200 is consuming power
> > without really doing any work. I want to put the unit in an 'low
> > power' mode (the ep9302 has support for this but how do I do it from
> > Linux?) during the 2.5 hr break between data acquisition cylcles.
> >
> > Any ideas on how I can acheive it?
> >
> > I went through the linux literature and found 'apm' (basically for
> > laptops), but would it work on the TS7200 (if I compiled it for
TS7200)?
> >
> > Thanks and with regards,
> > - Nagi
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
>
>
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