Re: how to limit a CPU temperature?
On 4/8/23 20:11, Mark Allums wrote:
On 4/8/2023 8:01 PM, David Christensen wrote:
On 4/8/23 07:17, songbird wrote:
i have a program that has changed it's behavior to suddenly
become a CPU hog (while doing something simple like uploading
files for my website). probably a bug, but it got me to
wondering how i could limit the CPU temperature to a range
well below the maximum that kicks in by the CPU itself.
i have an intel processor and it has the MAX which does
prevent it from going higher (100C), but i'd like to keep it
at 70C or lower.
i've been trying to find anything that will let me set this
but no luck yet in my searches.
thanks! :)
songbird
Assuming the computer had a proper thermal solution when assembled,
the 100 C processor temperature indicates that the thermal paste
between the processor and its heat sink has gone bad. I suggest
replacing it with silver-based thermal paste.
New paste yes, silver no. That's out-of-date. Silver is conductive.
Silver paste is not superior to Thermal Grizzly Kryonaut or Arctic
(maker of the most popular silver paste) MX-6. You want non-conductive,
non-capacitive paste.
Mark Allums
Thank you for pointing out advances in thermal paste since the last time
I used such. STFW the two brands you mention do seem to be the current
"top of the charts":
https://en.wikipedia.org/wiki/Thermal_paste
https://www.tomshardware.com/best-picks/best-thermal-paste
https://www.tomshardware.com/news/artic-mx6-thermal-paste
https://www.thermal-grizzly.com/en/products/16-kryonaut-en
https://www.arctic.de/us/MX-6/ACTCP00079A
I agree that getting paste where it does not belong during installation
is a problem; thermally, electrically, and chemically. "non-conductive,
non-capacitive paste" should mitigate damage should this risk occur.
Thankfully, I have not created such a mess; and the ones I have cleaned
did no apparent damage.
The last time I installed (silver-based) thermal paste, I seem to recall
that the manufacturer's directions were to apply a bead the size of a
grain of long-grain rice to the center of the processor case and then
seat the heat sink straight down. I believe I took one such joint apart
shortly after installation, and the paste had spread into a circular
area with a diameter of ~80% of the processor top. I will be curious to
see the pattern after a long period of use, if and when I take one of
those joints apart again.
I do not want paste oozing out of the sides of the joint, so I have
resisted the urge to use more paste or enlarge the application pattern.
I do not want air bubbles, so I have resisted the urge to spread the
paste. However, Thermal Grizzly recommends this technique in their
application guide:
https://www.thermal-grizzly.com/images/downloads/TG-ApplicationShortGuide.pdf
I have installed a few Intel "boxed" processor kits that included heat
sinks and fans. The heat sinks had a fine pattern of thermal paste in
rows with empty furrows in between. The pattern covered the entire
mating surface. The paste was nearly solid and was silver in color.
Looking beyond spillage, putting a insulator (non-conductive thermal
paste) between two conductors (metal heat sink and metal processor case)
is how you form a capacitor:
https://en.wikipedia.org/wiki/Capacitor#Parallel-plate_capacitor
The simplest model of a capacitor consists of two thin parallel
conductive plates each with an area of A separated by a uniform gap
of thickness d filled with a dielectric with permittivity ε . It is
assumed the gap d is much smaller than the dimensions of the plates.
...
... the highest capacitance is achieved with a high permittivity
dielectric material, large plate area, and small separation between
the plates.
...
The maximum energy is a function of dielectric volume, permittivity,
and dielectric strength.
Following the link "permitttivity":
https://en.wikipedia.org/wiki/Permittivity
In electromagnetism, the absolute permittivity, often simply called
permittivity and denoted by the Greek letter ε (epsilon), is a
measure of the electric polarizability of a dielectric. A material
with high permittivity polarizes more in response to an applied
electric field than a material with low permittivity, thereby
storing more energy in the material. In electrostatics, the
permittivity plays an important role in determining the capacitance
of a capacitor.
So, it would seem that "non-capacitive" thermal paste is thermal paste
with low electromagnetic absolute permittivity.
Does anyone have any ideas or explanations regarding forming a capacitor
out of the processor heat sink and the processor case by using a
non-conductive paste versus forming an electrical connection by using an
electrically conductive thermal paste? Or, a "real world" joint using a
thermal compound with electromagnetic impedance that varies with
frequency and/or intensity of the imposed electromagnetic field?
Notably, at frequencies of 66 MHz (processor external bus) and ~1 to ~5
GHz (processor internal)?
David
Reply to: