How To: Properly Plan And Pick Parts For An Air-Cooled PC, Part 2
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Page 1:A Foundation For Case Cooling: Fans
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Page 2:Case Fans: Air Flow And Noise Level
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Page 3:Case Fans: Decoupling Done Right
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Page 4:Case Fans: Speed Control
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Page 5:Case Fans: Should You Worry About Positive Or Negative Pressure?
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Page 6:Case Fans: Recommendations
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Page 7:CPU Coolers: Selection And Installation
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Page 8:CPU Coolers: The Right Thermal Paste
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Page 9:CPU Coolers: Applying Thermal Grease
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Page 10:CPU Coolers: Initial Startup And Test Run
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Page 11:VGA Coolers: We Rescue A GeForce GTX 480
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Page 12:VGA Coolers: Single-Slot Whisper Cooler
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Page 13:Think About Cooling Early
CPU Coolers: The Right Thermal Paste
Is There Such A Thing As The Perfect Thermal Paste?
From the user’s perspective, we have to answer this question with an emphatic no. There are suitable and unsuitable, bad, run-of-the-mill, and excellent thermal pastes. Certain options are suitable for specific scenarios and a range of budgets.
There are two common categories of thermal compounds: metal-based and metal-free, each of which can be liquid, creamy, or almost solid. Specialty products like nano pastes, liquid-metal pads, and metallic liquid are intended for professionals with skills, experience, and occasionally even nerves of steel.
For the beginner, the number of options that are both easy to use and completely effective seems to be quite narrow. Based on our experience, the best pastes for a neophyte are the simple, semi-liquid ones. It doesn’t matter whether the paste is silver-based or loaded with nano ceramics. The achievable cooling performance is quite similar.
In order to test one high-end paste from the liquid-metal family, we had to replace Xigmatek's Aegir on our test bench, since liquid metal pastes cannot be used on a cooler with exposed flat heat pipes. This is due to the exposed aluminum.
Thus, we picked the Xilence M606 (which features fairly similar performance) teamed with the 2CF cooler, and tested a few of the currently-available thermal pastes.
Test Results for Six Thermal Pastes
Once again, we are using the test rig from Part 1 of this short series and an old AMD Athlon 64 FX-62 processor, which can operate at three distinct power levels. This processor makes it easy to evaluate paste performance at different thermal power levels. The test bed's case is closed, its power supply is at the bottom of the enclosures, and the case fan arrangement leads to negative air pressure (fans on top and in front).
Not unexpectedly, we see that the high-end paste achieves lower temperature than the solutions we'd consider ideal for beginnings by a margin of 3 to 5 kelvins.
It is worth mentioning that you can easy erase any benefit inherent to an enthusiast-class thermal compound by handling and applying it improperly. On the other hand, if you use a mainstream product properly, it'll give you solid results.
The Xilence X5 and the Arctic MX2 are both non-conducting liquid pastes, which can be applied and spread easily. Below 100 W thermal power, the X5 slightly beats the MX2. Above that, the picture changes and the MX2 takes the lead. But keep in mind that differences of 1 kelvin can barely be measured consistently anyway. Both products are inexpensive and easy to use. Since the Xilence X5 is also suitable for graphics cards, we chose the inexpensive X5 as a reference for other tests and recommend it.
The enclosed spatula is suitable for spreading the paste, but in the next section we will illustrate an even simpler and cleaner way.
- A Foundation For Case Cooling: Fans
- Case Fans: Air Flow And Noise Level
- Case Fans: Decoupling Done Right
- Case Fans: Speed Control
- Case Fans: Should You Worry About Positive Or Negative Pressure?
- Case Fans: Recommendations
- CPU Coolers: Selection And Installation
- CPU Coolers: The Right Thermal Paste
- CPU Coolers: Applying Thermal Grease
- CPU Coolers: Initial Startup And Test Run
- VGA Coolers: We Rescue A GeForce GTX 480
- VGA Coolers: Single-Slot Whisper Cooler
- Think About Cooling Early
Kind of disappointed that the process of aftermarket GPU cooling wasn't explained more. That is something I have never done before, but always wanted to try out on one of my older cards.
the trick is, that i did and do twist, BUT i double check how much paste there is on the heatsink and the cpu, if there is enough I then fix it up on both ends and press the 2 together and do small twist... in fact if you have it lapped, you can twist a bit and it starts to give some resistance... IMO this tells me that access paste has distributed even and any access is gone...
This works so well that you cant separate the heatsink and cpu if you try to pull it straight off most of the time, but have to switch and move it.
How do I know it works? wouldnt be getting the results i did.. my old 720 be unlocked 4 cores and running at 3.3ghz .. I recently replaced it recently with Noctura D14 and phenom II X6, that I dialed into 4.13ghz
but then again I would say don't do this at home :P (the way I do it works good enough when using thicker pastes, such as the arctic silver 5)
***I forgot to mention that this works for those heatsinks were you have a strap and not screws... I agree that those that have high pressure through screws you probably should not move or twist... but all those heatsinks that can create a lopsided effect due to the strap, this way works very well, especially when having thermal paste on both ends, and best way is to strap it down and take it apart, examine it and then fix it up add/remove any paste and place it back on.***
For the noob this is a good enough article...
Im curious although it wont have a large affect, if the CPU cooler fan would act like a puller if put on the left side whether it would hurt or help the memory temps
I remember reading that sleeve bearing fans should not be used horizontally, that shortens the life span of the fan and makes it noisier over time. Something to do with the fluid in the bearing. Other bearings don't have this problem.
I also remember watching a program on NatGeo on submarines. Apparently modern day subs use propellors with a large number of thin blades. This basically avoids pressure diferences between water in front of the blade (in the direction it's spinning), thus prevents excessive low pressure in the region through which a propellor has passed. This avoids small bubbles of steam from building up and then popping, causing noise.
Seeing that air is a fluid too, i wonder if a similar principal will apply to it. Of course, there wont be any air bubbles popping in air, but i'm wondering if turbulence has any role to play, since i assume more blades=less turbulence. not sure though.
dB(A) is the A-curve...what about the C-curve? That's got more bass, which may be audible as a hum...C-cure measurements seem to ba a decible or three higher than A...
If the fans are connected to the mobo, you could use SpeedFan too...
With respect to the positive pressure section:
You say it goes against natural convection. What if i set the front and side panel as intake and the rear and top fans as the exhaust? I'm assuming the PSU is bottom mounted. Would it still go against convection?
What about neutral air pressure?
If, for example, the cooler needs to be re-seated following improper installation, is it a good idea to use isopropyl alcohol (Doctor's Alcohol) to clean the CPU and heatsink?
Cooler Master fans are pretty good, their higher quality fans 120mm fans move 79 to 90 CFM, their 200mm megaflow moves about 110 CFM. In both cases, rated noise is 19 dB(A). however, no rubber screws or frame so a that's a con.
BTW there's no prob with exposed heatpipes and the Arctic Silver, is there?
I'm not sure about all the other questions, but i know 90% isopropyl alcohol will work to remove thermal paste. "Goof Off" or similar products are even better. Also, i'd suggest using a coffee filter to apply the alcohol or goof off and wipe away the paste. that's what i do, works every time.
Well...not THIN as in barely there thin but just enough to make lettering opaque, not completely covered.
I thought the paste is just to fill in cracks and imperfections on the heat sink and the surface of the processor...
also any word on Zalman's heat paste that comes in liquidy paste? it comes in a small bottle with a brush like nail polish...been using that all this time...
My own experience with a GTX 470 (from PNY) with a shroud showed an idle temperature abour 45-48 C. When I modded the card with a Zalman 2000F cooler the temperatures dropped to 30 C at idle. This (delta) temperature reduction was consistant for all uses: from idle to load. Similar loads produced temperatures that were 15-20 degrees C cooler with the case exhaust method over the shroud.
Just two weeks ago I added a second GTX 470 (from Galaxy) in SLI. This model has, what is touted to be, superior cooling to the reference design. It consistantly runs about 10 C hotter than the PNY cooled by thge Zalman aftermarket cooler at idle. Because of space considerations the shroud design had to be mounted above the case exhaust GPU. When the GPU load is increased the shroud design temperatures show a increase (delta) of 15- 20 C over the case exhaust. This is expected, as the top mounted GPU is the one with the major work load.
I ordered the mesh sided side door from Corsair (600T) to provide extra ventillation from a side panel fan blowing on the GPUs. If this configuration works, I expect a 5-7 degree C in the top mounted
GPU. I will be using the 200 mm fan (from Corsair) that was modded out from the top of the case when I replaced it with two 120 mm fans (from Xigmatek).
Just to give you an idea of how different Celsius are from Kelvin, if the table states 58 degrees using the Nanoxia Nano TF1000 and they are Kelvin and not Celsius, that would be -272.15C (or -355F). That thermal paste would be hella better than liquid hidrogen!
I still agree that "differences of 1 kelvin can barely be measured consistently".
All in all, I like this articles. Keep the simple and efficient articles coming. Also the "advanced techie" ones... explained for us illiterate ones.
For the negative pressure case:
While the top fan blowing upward does indeed support (rather than oppose) natural convection, this is not a trait of a negative pressure setup. This is a trait of proper fan orientation (cover in the last article). Negative pressure means fewer particles available to transfer heat to. Thus negative pressure opposes natural convection. Conversely, positive pressure with a more particles available to transfer heat to supports natural convection. A good example of a properly oriented positive pressure system is the Silverstone Raven 2/ Fortress FT02.
Again, the more of a vacuum you create, the fewer the particles available, the worse the heat transfer. As a side note, fans are noisier in a vacuum as well, but I'll let you look into that if you're interested. In the setup your have, orienting the top fan downward would suck in some of the exhausted heat back into the case, but that again is a fan orientation issue. Again, the cases mentioned above post some of the best video card temps in the industry (especially for external exhaust style cards).
You'll have to explain this one to me, but I suspect this is another fan orientation issue rather than a positive vs negative airflow issue.
Even with a dust filter, you have to understand that most cases aren't air tight. With negative pressure air will be drawn in through every crack, bringing dust with it.
For the positive pressure case:
There are many counter examples to this statement. I'll stick with the Silverstone Raven 2/Fortress FT02. Though I do agree that if you orient the top fan down in the example case to achieve positive pressure, the improper orientation with drop your cooling effectiveness.
Not sure this is true either. While you do have more particles to work with, negative pressure systems tend to be better at directing airflow. This makes it easier to direct the heat away from the video card and out of the case. Of course, their are positive pressure systems that can achieve this as well.
Only with an inappropriately oriented fan such as in the example you show. Not an inherent flaw of positive pressure systems.
Having a hard time seeing this as a negative to positive pressure systems. This allows you to put the air where it is needed. I tend to think of a negative pressure systems more intuitive ability to direct airflow as a positive. If anything, it just requires more thought. At the opposite extreme, highly negative pressure systems can suffer from air coming in holes in the case and going straight out without doing any effective cooling.
Again, you'll have to explain this one, though I suspect it is an orientation rather than pressure issue.
This is true, but can't be considered a downside to cooling, especially when you already think the positive pressure systems don't cool as well. Rather it is something to consider (along with the PSU) as you design your cooling system.
A true downside to positive pressure systems is that you can get areas where air simply stagnates and doesn't get drawn into the flow. This leaves you only marginally better off than straight convection cooling. A good positive pressure case will make sure that air is still flowing around the components that generate heat.
In my findings, the best results come from a slightly positive pressure case. These still benefit from being able to direct the airflow for optimum cooling, while preventing dust build up and removing the vacuum effect. Though I must admit, the Silverstone Raven series/Fortress FT02 cases seem to get around these issues while remaining highly positive pressure. That said, fan orientation is of far greater concern, and should be setup to direct heat out of the case smoothly as shown in your first article. Improperly oriented fans will far outweigh the benefits of positive/negative pressure systems. In other words, make sure the case is designed for the type of system you want to implement rather than forcing the system you want on a case that isn't designed for it.
Also, good post from JPF on 1st page, altough I disagree that the (very) small variation in pressure would do any measurable harm to heat transfer. Smaller density has a bigger impact in the heat transfer through conduction, not much in convection.
From my experience, I could see that negative pressure inside the case did generate better temperaturas (most likely because you're able to direct the air by positioning fans acordingly).
Also, to help explain why negative pressure seems to bring in less dust, notice that the air is moving slower the farthest you go away from the fans, and slower air brings less dust in.
More fans bringing air in = more speed = more dust.
Less fans (and negative pressure) don't automatically mean less air will go in, but it does mean the air will enter slower (but through every possible little crack).
Ofc, please feel free to correct me if I'm wrong.
"Be sure to set the T Junction correctly..."
Thanks, but how do we do that?
Anyway about case pressure, I tend to believe positive pressure is much better than negative. I was running negative for a while and it's so bad that the top fan on my Antec 900 couldn't push a small piece of paper in the air. I then turned off one of the exhaust fans and the paper flew off... so basically you definitely aren't going to help remove heat by having negative airflow if your fan can't even push enough air to move a small paper.
I'm currently running a front mounted 220 rad in push/pull, plus a 5th fan (Silverstone Air Penetrator) blowing at my 5850s (it's mounted using the "rear mount bracket" so it is spaced off the radiator by 2 fan widths). 5850s I switched coolers from stock (blower fans) to Scythe Setsugens (low profile with Scythe Slim fans) which reduced the noise. I also use a Scythe Slim on the side intake blowing at the gpus. With all that the cooler performance also increased over stock (with lower noise) - although without those 2 extra fans the cooling as a bit worse than stock.
Anyway I have temp probes setup (Scythe fan controller) for intake and exhaust temps. The intake is placed just in front of the radiator and the exhaust is just inside of the rear exhaust fan. Under normal usage the delta is about 3C, under gaming it's around 5C so not bad. I don't know if the probes are very well calibrated though, I haven't bothered to test that yet.
I'm also a little surprised about in Part 1 with the PSU bottom mount. Having an Antec 900 II the PSU has to act as an exhaust - you can't flip it without cutting the case. I assumed it was ok as it would help bring airflow along the bottom, although it does go opposite to the airflow of every other component. I guess I might have to try cutting a nice hole and flipping it over. That'll help cable management a little bit too haha.
I also think you are giving a little too much credit to convection. A 50rpm change in fan speed achieves more than convection every could. Convection helps passively cooled systems; in anything with a fan, convection is overshadowed.
I remember once when i had my old Athlon 64 3200+, i was checking why it was heating so much, I took the cpu cooler out and just then found I didnt have any thermal paste to put it back in... And it was some kind of holiday so it would take days for the shops to open again.. So i used oil (cooking oil) :P I monitored temps constantly, fearing i had made a huge mistake, but to my surprise, it worked great..! It even kept temps even lower than before! :P Played games and everything. A couple of days later i bought the paste and cleaned the mess, but temps didnt go any lower than with my "culinary fix"
It is the best way to achieve an even spread of the material with HDT type heatsinks, as recommended by Frostytech and many other hardware sites. Take my advice please, don't use the drop method with these type of HSF or you'll end up with an inefficient mess.
A difference of 1 Kelvin = A difference of 1 Celcius, the article said "differences of 1 kelvin" which is correct, there was only a difference of 1 Kelvin. Although I agree it is a bit weird changing between Celcius and Kelvin like that without any need.