Re: [gentoo-user] Re: kernel heat warnings at low temps

[Kent Fredric]

On 6/27/07, James Ausmus <james.ausmus@×××××.com> wrote:
> On 6/26/07, reader@×××××××.com <reader@×××××××.com> wrote:
> > Alex Schuster <wonko@×××××××××.org> writes:
> >
> > [...]
> >
> > > What has the hdd temp to do with cpu tmeprature?
> >
> > [...]
> >
> > > hddtemp and cputemp are completly and totally unrelated.
> >
> > [...]
> >
> > First ... thanks for the other tips..
> >
> > I think you fellows may have this a bit wrong.  I have three video
> > editing desktops all running win xp.  On them I use a piece of
> > software called `Hardware sensors monitor' or Hmonitor.
> >
> > I've noticed over time (mnths) that when the cpu gets hot, the hdd are
> > also at elevated temps.  Maybe not critical but well above where the
> > run normally.
> >
> > This is on three different midtower boxes, so I have surmized that
> > although the heating of cpu may not be related mechanically to hdd
> > temp, in fact they rise and fall together due probably to close
> > proximity and being contained in same box.
> >
> > I realize this is not a definitive experiment but for my uses it does
> > work like that.
>
> Just as a note on a possible explanation for your observations in your
> Windows boxes:
>
> Most likely (CMIIW), when you notice the CPU and HDD temps rise, you
> are actively doing video editing - a CPU and memory *and* hard drive
> intensive task. When hard drives are "driven hard", they heat up. When
> CPU's are "driven hard", they heat up. If the computers main
> functionality is a task that tends to "drive hard" both the CPU and
> the hard drive, then yes, you will see a correspondence in the CPU/HDD
> temperature patterns. However, this does not mean that you *cannot*
> drive the CPU hard without driving the HDD hard, and vice versa - just
> because the are both being driven hard when you do video editing does
> not mean that they are inextricably linked to each other in workload
> and temperature profile.
>
> What operations are being performed on your Gentoo box when you see
> these CPU temperature warnings?
>
> -James
>
>
> >
> > --
> > gentoo-user@g.o mailing list
> >
> >
> --
> gentoo-user@g.o mailing list
>
>

You can drive a CPU heavily without crunching disk IO, just windows
doen't do that so well ( espcially the case if you run out of ram and
drive into swap,.. which windows seems more predisposed to doing in my
experience ). You want an example of how to do this, then open any
high-level math software, ie: povray, video-encoding, compression,
SETI.

And you can drive hard-drives heavily without your CPU getting hot
too, I think its something related to DMA and the fact we no longer
use PIO ( well.. at least i hope not ), simply by performing
disk-to-disk transfers ( while there will still be a lot of CPU usage,
its still a bit less than you'd get without offloading ), this is
especially the case if you have a real RAID system and your doing a
RAID controlled mirror ( it has its own processor to control that )

The similarity in temperatures tho, may be related to the dynamics of
case design ( ill pretend to know what im talking about, im no
professor on this, but i have worked out how to cut degrees ).  In the
closed case, most of the time ( at least in my experience ) the
majority of hard-drive cooling is passive, relying soley on the
lone-case-fan by the CPU,  or even relying on the cooling fans in the
PSU, and generally, at least in all the tower PCS ive seen, the heat
flows out of the hard drives and over the CPU / Northbridge .

Often, this is a big sodding melting pot of heat, with your GPU just
under the northbridge, the CPU just up from the northbridge, that area
can get a bit heated, and the extra heat from the hard drives I
believe lowers the effectiveness of the CPU cooler somewhat. My
solution was not a very pretty one, but it works like a bloody charm.

I effectively made a breakout-box for my hard drives, ( well, 4 bars
of aluminium with holes in it for screwing them together ) with all
the hard drives mounted in parallel in a 'portrait' position. ( to
allow heat to flow up over the drives unconstricted ) and mounted 2
cooling fans on the sides to blow cool air over the hard drives and
back into the room  ( EM purists look away here .... ) basically
isolating the cooling systems as as not to be so codepenant. To do
this i need to have my case panels off 24/7, i admit, but my case is
so crap that keeping them on is too much effort.

In summary : CPU temp cannot be accurately measured with HDD sensor
probes, ...especially as CPU is up from hard drives in most cases, and
heat .. generally rises.
If console logs are complainging about CPU over-heat, then either its
overheating, your thresholds are too low, ...or whatevers doing the
measurement is broken.

If you cant find out from some in-linux tool what the problem is, ...
you may want to find some sort of alternative way of measuring
temperature ( ... laser thermometer might be an idea ... )

Either way, best of luck .
-- 
Kent
ruby -e '[1, 2, 4, 7, 0, 9, 5, 8, 3, 10, 11, 6, 12, 13].each{|x|
print "enNOSPicAMreil kdrtf@×××.com"[(2*x)..(2*x+1)]}'
-- 
gentoo-user@g.o mailing list