Thermal pad or Thermal paste?

[Nick M V Salmon]

Ya know, measuring the distance between stars in inches isn't really practical
but if you're off by .1 parsecs when you get there that last step off the ladder
ain't going to be just 'one small step for a man' whether it's a "single digit
number" or not.

<LOL>

[UK]_Nick...

 

[David Maynard]

Dansdata.com does provide a watts number. Unfortunately it
must calculated from his data.

The only numbers provided are C/W. Neither watts or temperatures are derivable
from those numbers.

I believe it was also provided
in another article about this same test.

There wasn't a link to 'another' article and I can only go by what was there. He
did, however, mention he changed it from his 'normal' setup.

He was using a
constant 50 watt heat source which is typically equivalent to
a 65 or 75 watt CPU.

A 'what' CPU?

Both AMD and Intel give power dissipation requirements and the maximum for an
AMD XP3200 is 76.8 Watts. The thermal design power spec for an Intel 3.06 Gig is
81.8 watts. That's straight HEAT, not some 'typically equivalent' invention of
yours. My example with 70 watts was not out of range, not to mention I included
numbers for 55W and 35W (35W being about right for a 1.4 gig tualatin celeron).

From his data, thermal compounds resulted in a 9 degree
reduction of CPU temperature.

Not from the data in THAT article.

As kony has demonstrated, this
would probably be less if the heatsink was smooth; not
concentric rings.

Probably, but that doesn't alter the fact that your characterization of what HE
said is inaccurate.

And there was virtually no difference
between Arctic Silver and all other thermal compounds.

Which, btw, were all 'grease' type materials in that they were not pads (the
topic of this thread)

It's also not the topic you keep trying to promulgate.

But
demonstrated is that thermal compound only results in, at
best, single digit temperature reductions.

False, and I posted the numbers which prove it. Take the top end XP or P4 power
numbers and it would be even larger than the BIGGER THAN A SINGLE DIGIT one I
posted for 70 watts.

Not to mention all I have to do is state temperatures in F to ruin your 'single
digit numbers' claim for 9C.

Even with a worse case heatsink surface of concentric rings
(not smooth), the thermal compound only resulted in single
digit temperature decrease. Thermal compound would only be
less effective had that heatsink surface been smooth.

And I've posted specific, and numerical, analysis of thermal budgets which show
'single digit numbers' are significant.

I would have though my .1 parsec joke would have driven home the point that
broad brush euphemisms like 'single digit number' don't mean anything.

 

[w_tom]

A 65 or 75 watt CPU typically outputs about 50 watts. One
with numerical experience and heatsinks would know this.
David Maynard is only just learning these numbers exist. So
he posts this in error:

If we plug a 70 watt CPU into those numbers the temperature
improvement would be 12.6C

0.66 - 0.48 is 0.18. A 70 watt CPU (maximum power)
outputs typically about 46 to 52 watts; or 50 watts. David
would know this if he had heatsink design experience. 9
degree difference - a single digit difference. And that
difference would be even smaller if tested heatsink provided a
better interface surface as kong demonstrated. A better
heatsink surface means even higher wattage CPUs still only
output single digit temperature differences - not important to
the average CPU user.

David Maynard assumes a 70 watt CPU outputs 70 watts
constant because these numbers and calculations are new to
him. IOW he wants to argue.

Fact stated - thermal compound only results in single digit
temperature decreases. Dansdata.com demonstrates same using a
heatsink that does not even have a good surface. With or
without thermal compound are both valid options when
assembling a CPU to heatsink. Either will provide sufficient
CPU cooling even if run on a 100 degree F room. Important is
the 'degree C per watt' rating on that heatsink - use of
thermal compound is but a secondary consideration.

kony demonstrated even less advantage to thermal compound
when he lapped a heatsink surface. Bottom line, thermal
compound makes but a minor temperature improvement - which is
contrary to many widely touted legends.

A 9 degree difference is not significant - except when
overclocking. Those nine degrees would be even less using
a heatsink with better surface. That was posted previously
which leaves me to wonder why so much naysaying - without
supporting facts - and without comprehending a difference
between typical and maximum CPU watts. I am left to assume
another only wants to argue.

Dansdata.com demonstrates what kony also demonstrated and
what is obvious from calculations. Thermal compound is not
essential to CPU operations - except maybe for the
overclocker.

Following points were summarized in a post on 7 Sept, and
are posted again for the benefit of lurkers who have been
confused by all this naysaying supporting facts or correct
numbers:
1) that thermal compound must be applied so sparingly that CPU
makes mostly a direct contact with heatsink. So little
thermal compound that it does not spread much into the outer
half of CPU.
2) if heatsink is properly machined, then heatsink can be
applied to CPU without any thermal compound. If properly
machined, then thermal compound would only result in single
digit temperature decreases.
3) many heatsinks are sold even without the essential "degree
C per watt" number. Many don't even know how good their
heatsink really is OR how much better it would be if properly
mated to CPU. That test first without thermal compound, then
with goes a long way to learning how good a heatsink really
is.
4) Arctic Silver is overhyped. Most thermal compounds do for
dimes what Arctic Silver does for dollars. But then Arctic
Silver also does not make numerical specifications easily
available - which should be the first indicator that Arctic
Silver is hiding something. Products sold without numerical
specs should be routinely suspect. Arctic Silver is mostly
sold on hype - engineering specs be damned when your customers
too often fear the numbers.

 

[David Maynard]

A 65 or 75 watt CPU typically outputs about 50 watts. One
with numerical experience and heatsinks would know this.
David Maynard is only just learning these numbers exist.

Maybe some day you'll learn to read a spec sheet before you make an even bigger
fool of yourself than you have already.

Intel® Pentium® 4 Processor with 512-KB L2 Cache on 0.13 Micron Process: April
2003 Document Number: 298643-008

5.1 Thermal Specifications
Table 5-1 specifies the thermal design power dissipation envelope for the
Pentium 4 processor with 512-KB L2 cache on 0.13 micron process.

Table 5-1. Processor Thermal Design Power

Processors with Thermal Design
multiple VIDs Power1,2 (W)
..
..
..
3.06 GHz 81.8

Processors with
multiple VIDs for 800 MHz
system bus
..
..
..
3 GHz 81.9

That's heat dissipation the thermal solution should be capable of handling. It
is NOT the electrical power requirements, which I presume is what you think "70
watt CPU" means; those are in section 2.11.

So
he posts this in error:



0.66 - 0.48 is 0.18. A 70 watt CPU (maximum power)
outputs typically about 46 to 52 watts; or 50 watts.

I wasn't talking about whatever you think a "70 watt CPU (maximum power)" is. I
told you specifically which ones, by manufacturer and model number, and the heat
they generate according to the manufacturer's spec sheet; or can't you read?

David
would know this if he had heatsink design experience. 9
degree difference - a single digit difference.

Wrong. .18C/W times 70 watts is 12.6C. As I said, if we used the Intel numbers
for a 3.06 Gig P4, I.E. 81.8W, it would be even more.

And if you weren't such an ass you'd have noticed I also included calculations
for 55 watts and 35 watts to show what the numbers would be over a range of
CPUs, and then showed their relevance to the thermal budget; even when "single
digit".

And that
difference would be even smaller if tested heatsink provided a
better interface surface as kong demonstrated. A better
heatsink surface means even higher wattage CPUs still only
output single digit temperature differences - not important to
the average CPU user.

It's only important if they want it to work per specifications.

Of course, then there's the point that your incessant claim "single digit"
numbers are "not important" is utter nonsense.

David Maynard assumes a 70 watt CPU outputs 70 watts
constant because these numbers and calculations are new to
him. IOW he wants to argue.

Wrong. I listed the specific CPUs and gave the manufacturer's number for their
thermal dissipation, not based on them being an 'X watt CPU', in terms so clear
that even a room temperature IQ could follow it so I don't know why you failed
to grasp it.

 

[larrymoencurly]

Author provides numbers with his results for heatsink bare
verses heatsink with thermal compounds:
http://www.dansdata.com/goop.htm

His copper heatsink also had concentric ridges which were not
removed. And yet thermal compound resulted in only single
digit temperature improvements.

If thermal compound doesn't matter much, why do all CPU manufacturers
include something like it with their retail boxed CPUs and heatsinks?

The retail boxed AMD XP1800+ I bought last month cmae with a layer of
phase change material on its heatsink, and my old 300 MHz Slot 1 Intel
Celeron heatsink, which was installed at the factory, had grey grease
on it. Both heatsinks were fairly flat, although I didn't measure
this.

 

[Strontium]

Tom's an idiot. Any more questions?

-
larrymoencurly stood up at show-n-tell, in
(e-mail address removed), and said:

 

[w_tom]

Can you guarantee that one will mount every CPU properly? I
too would recommend hobbyists use thermal compound. The stuff
is so cheap. So many computer assemblers make mistakes. Best
to just tell them to always use thermal compound. However CPU
manufacturers have provided some CPU heatsink assemblies
without thermal compound when customer assembly was not
required.

Too many computer assemblers completely avoid numbers such
as the essential "degree C per watt" parameter. Better to
tell them to install thermal compound to help compensate for a
poorly surfaced or not even machined heatsinks. To
compensate for heatsinks erroneously selected on hype, price,
or a useless parameter such as CFM.

Just because cheap thermal compound is used does not prove
that thermal compound is required.

Furthermore, a recent Intel paper demonstrated little
difference between thermal compound and bare 'heatsink to CPU'
for high power semiconductors. In that same paper, Intel also
demonstrated advantages of phase change material. But those
numbers are beyond the scope of where this discussion has
proceeded. This discussion demonstrates how to experiment -
to learn heatsink interface quality by running without and
then without thermal compound. This discussion debunks myths
about thermal compound being 'essential' by providing both
underlying theory and experimental examples. This discussion
demonstrates why specifications are so important in thermal
analysis and which specifications are important.

A "degree C per watt" specification is more important than
thermal compound. Specifications associated with that "degree
C per watt" parameter demonstrate pros and cons of thermal
pads, thermal compound, and heatsink quality. Nothing from
Intel or AMD 'instructions for assemblers' proves that thermal
compound is essential. If thermal compound was essential,
then one would have easily provided those numbers days ago.

 

[w_tom]

Without specifications, that post is just another junk
science proclamation. But then too many use such junk science
logic which also makes Arctic Silver so profitable for its
manufacturer.

 

[larrymoencurly]

If thermal compound doesn't matter much, why do all CPU
manufacturers include something like it with their retail
boxed CPUs and heatsinks?
my old 300 MHz Slot 1 Intel Celeron heatsink, which was installed
at the factory, had grey grease on it. [Heatsink was] fairly
flat, although I didn't measure this.

Can you guarantee that one will mount every CPU properly? I
too would recommend hobbyists use thermal compound. The stuff
is so cheap. So many computer assemblers make mistakes.

I don't think that it's even possible to mount a Pentium4 heatsink
improperly because of the widely-spaced supports, and with an Athlon
improper mounting either causes the center part to be cracked or the
CPU to burn up right away because of a big gap with the heatsink. But
what about the example I mentioned previously, where the Slot 1
Celeron came with a factory-installed heatsink with thermal compound
on it?