Re: [opensuse] Unstable system - who is the culprit?
- From: Aaron Kulkis <akulkis00@xxxxxxxxxx>
- Date: Thu, 14 Feb 2008 15:32:00 -0500
Mike wrote:
On Thursday 14 February 2008 15:54, Per Jessen wrote:
OK, yesterday morning I moved the box outside, hooked it up with
network and power. Outdoor temperature was -1C .
Temperature rose to about 6 in the afternoon, but the machine
actually ran pretty stable throughout the day. I had one lockup
which needed a hard reset, but I haven't been able to reproduce that.
Whilst running 4 x mprime, the temperatures as seen by sensors
stabilised at this:
work System CPU temp3 Outdoor
4 mprime 39 51 81 5
4 mprime 35 50 80 6
So it's all about cooling. The interesting thing is - the machine
uses the AMD supplied CPU heatsink and fan. It's got additional fans
and heatsinks to improve the air/heat flow. How do I improve on the
cooling without looking at water-cooling and such?
The first thing I always do is get rid of the AMD supplied fans. I've used Thermaltake type heatsinks and fans. I know that Coolermaster and Thermaltake make pretty good equipment for CPU cooling.
How big is your case? Midtower, full tower?
Well - the system remains unstable and automatically reboots after a
while, maybe 10-15mins, of running 4 x mprime. I've already got an
RMA# so I think this board is going back after all.
Could be the problem.
Also remember..
Fans at the bottom of the case blow inwards.
Fans at the top of the case blow outwards.
In a quiescent state, CFM in = CFM out
[CFM = Cubic Feet/Minute = (ft^3)/minute,
essentially the same as m^3/minute except
for a dimensionless conversion factor of
about 30.
or, to make it more clear
CFM in = CFM through = CFM out.
This is an application of Thevenin's
Current Rule and is practically a mathematical identity.
This is an identity. if CFM in > CFM out, the case would
eventually explode; conversely, if CFM in < CFM out, then
eventually the case would be completely evacuated).
What does this mean?
If you have 1 fan blowing in rated at 300 CFM, and 2 case
fans and a PSU fan blowing out, each rated at 300 CFM,
then initially, the out fans will blow out 600 CFM more
than the in fans, until the air pressure inside the case
has dropped enough that... the in-fan is bring in a little
more than 300 CFM...and the out-fans are blowing out a
bit more than 300 CFM total (a little over 100 CFM each,
1/3 of their rating!). Additional in-flow might be
provided by leaks or ventilation holes in the case.
In any event in the above scenario, the air pressure
in the case is low, which means that any fans and heat
sinks used inside the case for CPU cooling, etc are
operating in an environment in which there is less
air density than the thing is designed for, and will
therefore not cool as well as if there was more
air inside the case.
If the situation is reversed (3 fans blowing in, 1 PSU
fan blowing out), we still get to the same quiescent
state of the flow-through being slightly higher than
the flow rate provided by one fan. Initially, the
in-fans blow 900 CFM in, while the out-fan blows out
only 300 CFM...but as internal air pressure RISES,
the input fans flow rapidly drops to about 100 CFM each
(again), and the out-fan now runs slightly above rated
capacity (a bit over 300 CFM).
But now...the air WITHIN the case is under increased
pressure. The CPU fan is blowing MORE air molecules
over the heat sink...therefore IMPROVING the cooling
ability of the heat-sink/fan apparatus.
In this second example, using case perforations for
more air flow is more acceptable than in the first
example... In both examples, the air flow through
performations only happens due to a difference in
air pressure inside the case vs. outside the case,
but in the second example, the perforation air-flow
is due to higher air pressure (and thus, higher air
density inside the case), while in the first example,
the perforation air flow is due to a vacuum condition
inside the case, which is detrimental to cooling
the CPU heat sink -- vacuum conditions within the
case should always be resolved by increasing the
amount of air forced into the case.
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- References:
- [opensuse] Unstable system - who is the culprit?
- From: Per Jessen
- Re: [opensuse] Unstable system - who is the culprit?
- From: Per Jessen
- Re: [opensuse] Unstable system - who is the culprit?
- From: Per Jessen
- Re: [opensuse] Unstable system - who is the culprit?
- From: Mike
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