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12-core AMD 3900X - does it need better cooling?



 
 
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  #1  
Old November 11th 19, 11:21 PM posted to alt.comp.hardware.pc-homebuilt
John Savard
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Posts: 7
Default 12-core AMD 3900X - does it need better cooling?

The recent announcement of the 3950X from AMD startled me.

Unlike the other new Ryzens, it doesn't include a Wraith cooler in the box.
Instead, it is recommended that at least a 280mm AIO cooler be used with it.

Not being an overclocker, I had to do some web searching to get a feel for what
was being referred to.

What I found out was:

An AIO cooler is a water cooler that comes with the radiator, the tubes, and the
water block all in a single unit. (You might still have to screw the fans on
yourself.) Not much chance of a leak, no need to periodically top up the fluid.

The 280mm dimension refers to the length of the cooler. A two-fan cooler will
typically be 240mm, and a three-fan cooler 360mm, the fans being 120mm square,
but there are extra-wide two-fan coolers.

My case has two holes in the back of it - for the more expensive and dangerous
custom water-cooling solution. I'm not sure where in the case I would mount the
fans of an AIO.

But then I've only got a 12-core 3900X, not a 16-core 3950X. Supposedly, the
Wraith cooler is good enough for that.

Not only did the 3950X announcement raise some doubts, in my searches I found
that with the stock cooler temps on a 3900X can go up to 95 degrees Celsius.
Apparently the chip can survive that. But I'd like to prolong the chip's life.

So I also looked into high-end air coolers. Mind you, the Wraith cooler looks
pretty impressive to me already. Would a fancy air cooler really be better?

One comparison of the best air and water coolers showed an air cooler - a Noctua
that was one tier down from the top end, a #14 with two heatsinks but only one
fan - as sneaking into 360mm AIO territory.

So maybe the two that I'm considering, that are available at my local computer
store, are both reasonable choices (they mount on Threadrippers as well as
AM4)...

the Noctua NH-D15, and the Phanteks PH-TC14PE. These are both their respective
manufacturers' top-of-the-line air cooler models, with two fans and two
heatsinks.

They're basically similar to another air cooler I saw in a video about someone
taking apart a video card and replacing the existing fans with a fancy air
cooler (DeepCool Assassin III).

https://www.youtube.com/watch?v=m3YnpwAAHhM

DeepCool products are (or at least _were_) sold under the name Logisys in the
United States.

John Savard
  #2  
Old November 12th 19, 04:55 AM posted to alt.comp.hardware.pc-homebuilt
Paul[_28_]
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Posts: 1,467
Default 12-core AMD 3900X - does it need better cooling?

John Savard wrote:
The recent announcement of the 3950X from AMD startled me.

Unlike the other new Ryzens, it doesn't include a Wraith cooler in the box.
Instead, it is recommended that at least a 280mm AIO cooler be used with it.

Not being an overclocker, I had to do some web searching to get a feel for what
was being referred to.

What I found out was:

An AIO cooler is a water cooler that comes with the radiator, the tubes, and the
water block all in a single unit. (You might still have to screw the fans on
yourself.) Not much chance of a leak, no need to periodically top up the fluid.

The 280mm dimension refers to the length of the cooler. A two-fan cooler will
typically be 240mm, and a three-fan cooler 360mm, the fans being 120mm square,
but there are extra-wide two-fan coolers.

My case has two holes in the back of it - for the more expensive and dangerous
custom water-cooling solution. I'm not sure where in the case I would mount the
fans of an AIO.

But then I've only got a 12-core 3900X, not a 16-core 3950X. Supposedly, the
Wraith cooler is good enough for that.

Not only did the 3950X announcement raise some doubts, in my searches I found
that with the stock cooler temps on a 3900X can go up to 95 degrees Celsius.
Apparently the chip can survive that. But I'd like to prolong the chip's life.

So I also looked into high-end air coolers. Mind you, the Wraith cooler looks
pretty impressive to me already. Would a fancy air cooler really be better?

One comparison of the best air and water coolers showed an air cooler - a Noctua
that was one tier down from the top end, a #14 with two heatsinks but only one
fan - as sneaking into 360mm AIO territory.

So maybe the two that I'm considering, that are available at my local computer
store, are both reasonable choices (they mount on Threadrippers as well as
AM4)...

the Noctua NH-D15, and the Phanteks PH-TC14PE. These are both their respective
manufacturers' top-of-the-line air cooler models, with two fans and two
heatsinks.

They're basically similar to another air cooler I saw in a video about someone
taking apart a video card and replacing the existing fans with a fancy air
cooler (DeepCool Assassin III).

https://www.youtube.com/watch?v=m3YnpwAAHhM

DeepCool products are (or at least _were_) sold under the name Logisys in the
United States.

John Savard


The thing that makes an air cooler work, is the heat pipes.

The heat pipes are "phase change", and there is a liquid and
and a vapor phase inside the pipe. The "heat of vaporization"
is a powerful driver for thermal flux. A heatpipe can move
more heat, than a solid copper tube of the same diameter,
many times over.

The purpose of the heatpipe then, is to transport heat into the
cooling fins. The fins have thermal resistance, and if the fin
is "too long", the tip of the fin will be cold, because the
heat doesn't travel up there all that well.

So if you started with a Noctua "cubic foot of fins" and had
no heatpipes, it would be virtually worthless. Only about an inch
to two inches of fin, near the CPU, would provide cooling. The
rest of the fins would be deadweight.

By weaving heatpipes through the fin assembly, the thermal resistance
of the pipe is "zero", and then the "fin length" is measured from
where it touches the pipe.

I have the Noctua NH-D15 here, on a 156W (measured) processor.
I only use the center fan. And I have a home-made "stand" that
sits underneath the Noctua, to push up against the force of
gravity. This is intended to take some stress off the socket.
Not everyone will particularly care to do that, so this is
just an experiment on mine. It makes it inconvenient to put
cards into slots - if I had to do it again, I'd make a frame
anchored to the top of the case.

The other part of the solution, is the rear cooling fan.
A Noctua by itself, would smother under the "cloud" of hot
air it makes. Initially I started with a 110CFM fan on
the back (with a speed controller and turned down),
but even turned down it was still too loud. I went from
the large fan, to a thinner fan, and still got decent
performance.

My processor "hasn't had a hot day in its life", so
air for me, was an OK choice. If you're an overclocker,
lock all the cores, or use some exotic setting, it's
always possible to have a huge power dissipation on
the CPU. Then perhaps that air solution would not be
enough. (Like, if your motherboard BIOS has a setting
to defeat the power limiter.)

*******

Regarding the large coolers, some computer cases have
a bay at the top, and the cooler blows its exhaust air upwards.
There's room for at least a two-fan cooler. I don't
know if a three-fan cooler would fit.

The PSU in those cases, sits at the bottom of the case,
out of the way. You would still benefit from a rear
exhaust fan, in situations where the video card is
not similarly cooled, and the video card has
contributed to a "hot cloud" near the back
of the case.

The notion of an AIO that blows hot air around inside
the case is silly. You want cooling solutions where
if there is to be a fan, it moves the air outside the
case immediately. If I had a liquid loop, I'd probably drill
some holes in the back of the case, and run the plumbing
for an external radiator.

Whereas heatpipes operate on "phase change", liquid
coolers always work with liquid, and the amount of
heat flux the liquid can carry, isn't quite the same
as a heat pipe. In some situations, the diameter of the
plumbing has to go up, to be able to carry enough
"liters per second", to get the desired cooling effect.

You use whatever metrics are available, and do the maths.
If an air cooler states a "max watts", that avoids doing
maths and it also prevents doing maths. If the air cooler
has a theta_R, you can work out what the delta_T will be,
for a given amount of heat from the watts of electricity.

I don't know what kind of rating scheme they use with
liquid coolers. There's a thermal resistance (so there would be
a theta_R), but the elements in the loop, the plumbing
diameter, pipe length, probably factor into the math too.
And the radiator size, number of fans (air velocity in LFM),
would all play a part in determining how much heat the
radiator can remove from the fluid before it heads
back to the CPU.

*******

https://www.anandtech.com/show/14605...ing-the-bar/19

"Package Power Tracking (PPT):

The power threshold that is allowed to be delivered to the socket.

This is ... 142W for 105W TDP processors.
"

That says (in my opinion), the NH-D15 would be fine.
And probably fine, with just the center fan installed.

It should not be hitting 95C with that thing on it, unless
you turned off the rear fan on the computer case and
the air was dead around the cooler.

But also consider the heat dumped by the video card.
If your project needs a 1200W PSU, then you'll need
a more fancy solution. I think mine runs off a 550W
supply, and draws over 300W on Furmark. (I haven't
tried Furmark and Prime95 together yet... I could
probably drive it to around 390W if there weren't
limitations.)

When shopping for a motherboard, make sure the VCore
has a decent heatsink on it. That's the mistake I
made on my build. I didn't notice when I bought it,
that the VCore heatsink was too small. While testing
with the motherboard sitting on the kitchen table,
I burned myself on the VCore cooler. When I assembled
the system in the case, I added a fan just for VCore.
(That's why you test on the kitchen table first,
to spot deficiencies before assembly.)

Paul
  #3  
Old November 12th 19, 03:31 PM posted to alt.comp.hardware.pc-homebuilt
John Savard
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Posts: 7
Default 12-core AMD 3900X - does it need better cooling?

Thank you for your helpful information.

Since my post, I've found some interesting things from some additional research.

Going up from the stock Wraith cooler on a 3900X will only produce slight
additional performance, but it will make the chip cooler, from about 93 degrees
C to about 75 degrees C.

However, another article notes that even at 60 degrees C, chip lifetime is being
shortened, although not as much as at higher temperatures. Ideally, one would
like 50 degrees C.

A 360 mm AIO is what got down to 75 degrees C or so, and that's the best
commercially available cooling solution other than potentially leaking and
expensive watercooling kits. There's just no mainstream cooling solution that
would achieve the goal of indefinite lifespan and full performance.

Not that I'm going to have to worry about this for a while. Even after I make
the new build my daily driver, I won't be pushing it hard for months, until I
figure out something worthwhile to do with it.

John Savard
  #4  
Old November 12th 19, 08:49 PM posted to alt.comp.hardware.pc-homebuilt
Flasherly[_2_]
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Posts: 2,407
Default 12-core AMD 3900X - does it need better cooling?

On Tue, 12 Nov 2019 06:31:27 -0800 (PST), John Savard
wrote:

Since my post, I've found some interesting things from some additional research.

Going up from the stock Wraith cooler on a 3900X will only produce slight
additional performance, but it will make the chip cooler, from about 93 degrees
C to about 75 degrees C.

However, another article notes that even at 60 degrees C, chip lifetime is being
shortened, although not as much as at higher temperatures. Ideally, one would
like 50 degrees C.

A 360 mm AIO is what got down to 75 degrees C or so, and that's the best
commercially available cooling solution other than potentially leaking and
expensive watercooling kits. There's just no mainstream cooling solution that
would achieve the goal of indefinite lifespan and full performance.

Not that I'm going to have to worry about this for a while. Even after I make
the new build my daily driver, I won't be pushing it hard for months, until I
figure out something worthwhile to do with it.

John Savard


On an ideal MB, a few being presumably within this discussion, what
balances remain are between revisions of W10 and AMD "power balance"
plans -- the 50C- being evident, at least by some reports, although at
a low/thread idle/state, apparently without, especially, undue cooler
considerations overall. Ideally, how hard and long and at what
cut-off limits is then within an adjustable leeway otherwise from
exceeding a satisfactory ambient/idle state where chips virtually last
forever.

https://community.amd.com/thread/241414
  #5  
Old November 12th 19, 08:55 PM posted to alt.comp.hardware.pc-homebuilt
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default 12-core AMD 3900X - does it need better cooling?

John Savard wrote:
Thank you for your helpful information.

Since my post, I've found some interesting things from some additional research.

Going up from the stock Wraith cooler on a 3900X will only produce slight
additional performance, but it will make the chip cooler, from about 93 degrees
C to about 75 degrees C.

However, another article notes that even at 60 degrees C, chip lifetime is being
shortened, although not as much as at higher temperatures. Ideally, one would
like 50 degrees C.

A 360 mm AIO is what got down to 75 degrees C or so, and that's the best
commercially available cooling solution other than potentially leaking and
expensive watercooling kits. There's just no mainstream cooling solution that
would achieve the goal of indefinite lifespan and full performance.

Not that I'm going to have to worry about this for a while. Even after I make
the new build my daily driver, I won't be pushing it hard for months, until I
figure out something worthwhile to do with it.

John Savard


It could be, the performance is a function of the TIM
used under the lid. You'd need to see a picture from
a de-lidding sequence, to see what they used.

https://cdn.mos.cms.futurecdn.net/EF...eNB-650-80.jpg

https://images.anandtech.com/doci/14...52_678x452.jpg

Paul
  #6  
Old November 15th 19, 04:05 AM posted to alt.comp.hardware.pc-homebuilt
John Savard
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Posts: 7
Default 12-core AMD 3900X - does it need better cooling?

On Tuesday, November 12, 2019 at 12:49:13 PM UTC-7, Flasherly wrote:

On an ideal MB, a few being presumably within this discussion, what
balances remain are between revisions of W10 and AMD "power balance"
plans --


I've continued researching information.

Looking for a better cooler, I found the Phononics HEX 2.0. This was an air
cooler with one fan and two cooling towers. However, only one tower had its heat
pipes going to the plate touching the chip. The other tower had its heat pipes
going to a plate that had a thermoelectric element between it and the first
plate.

I was interested. Unfortunately, this cooler wasn't very successful; for most
users, it would have only been slightly better than less expensive coolers. As I
wanted to keep the chip really cool, it might have been more useful to me. But
because it wasn't successful - it wasn't followed up with a newer model; this
one doesn't have mounting hardware for the AM4 socket.

And I found *another* similar cooler, based on the same two-plate design, from
2007, the Ultra ChillTec.

However, now that the latest version of Ryzen Master allows one to select an
"Eco Mode" for the chip - well, giving up a little performance to extend chip
life is reasonable, so I don't need to look for some amazing super cooler.

John Savard
  #7  
Old November 15th 19, 05:13 AM posted to alt.comp.hardware.pc-homebuilt
John Savard
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Posts: 7
Default 12-core AMD 3900X - does it need better cooling?

Even the Noctua NH-D15 and the Phanteks PH-TC14PE don't have AM4 mounting
hardware. At my local computer store, only smaller air coolers have AM4 mounting
hardware - and, also, high-end AIO coolers, so at least 3950X owners have
something available.

John Savard
  #8  
Old November 15th 19, 05:24 AM posted to alt.comp.hardware.pc-homebuilt
John Savard
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Posts: 7
Default 12-core AMD 3900X - does it need better cooling?

Checking out the Noctua site, NH-D15s made in 2019 and later have had AM4 mounting
hardware added. But old stock won't have it.

The Phanteks site didn't specify what sockets their cooler supported at all, it
just named the supplier of the mounting hardware.

John Savard
  #9  
Old November 15th 19, 05:35 AM posted to alt.comp.hardware.pc-homebuilt
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default 12-core AMD 3900X - does it need better cooling?

John Savard wrote:
Checking out the Noctua site, NH-D15s made in 2019 and later have had AM4 mounting
hardware added. But old stock won't have it.

The Phanteks site didn't specify what sockets their cooler supported at all, it
just named the supplier of the mounting hardware.

John Savard


https://noctua.at/en/nm-am4-mounting-kit

"Owners of Noctua CPU coolers* can obtain the NM-AM4 Mounting-Kit
free of charge via this form. A proof of purchase (electronic version,
photo or scan of the invoice) of both a Noctua CPU cooler and either a
socket AM4 mainboard or socket AM4 CPU are required."

Paul
  #10  
Old November 17th 19, 04:54 AM posted to alt.comp.hardware.pc-homebuilt
John Savard
external usenet poster
 
Posts: 7
Default 12-core AMD 3900X - does it need better cooling?

On Thursday, November 14, 2019 at 9:35:41 PM UTC-7, Paul wrote:
John Savard wrote:
Checking out the Noctua site, NH-D15s made in 2019 and later have had AM4 mounting
hardware added. But old stock won't have it.

The Phanteks site didn't specify what sockets their cooler supported at all, it
just named the supplier of the mounting hardware.

John Savard


https://noctua.at/en/nm-am4-mounting-kit

"Owners of Noctua CPU coolers* can obtain the NM-AM4 Mounting-Kit
free of charge via this form. A proof of purchase (electronic version,
photo or scan of the invoice) of both a Noctua CPU cooler and either a
socket AM4 mainboard or socket AM4 CPU are required."


I've kept the reciept from my 3900X, so that is an option. At this point,
though, it appears that using Eco Mode in Ryzen Master and keeping the stock
cooler is more likely to achieve my goals, and it will also save me the trouble
and risk of hooking up the motherboard again. I think the NH-D15 will fit in my
case, but I'm not 100% sure.

I mean, I could also buy a 360mm AIO which does come with AM4 mounting hardware
in the box. There, the problem would be that I am not sure I could find a good
spot for the radiator.

John Savard
 




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