Cooling FAQ

[whetu]

Cooling:
Last updated: 24/10/2003
(over 12k views since 07/02)

Preamble:
The purpose of this FAQ is to educate in the basics of cooling. This FAQ aims to give cooling newbies a solid background in cooling theory and methodologies before they even open their case.

This FAQ assumes you have a basic knowledge of computer hardware.

Disclaimer:
Overclockers New Zealand, the author of this FAQ, and everybody else on this planet do not take any responsibility for any damage caused by you in the course of overclocking and cooling. Overclockers New Zealand does not guarantee authenticity of the information provided in this FAQ. The FAQ author agrees that all information within this FAQ is provided on a "to the best of my knowledge" basis.

Readers of this FAQ accept that this document is for educational purposes only, and that further research is a requirement before cooling is to be attempted. Readers of this FAQ also agree that no responsibility will be held by Overclockers New Zealand or the FAQ author. Readers of this FAQ accept complete and full responsibility for their mistakes.

Introduction:
Cooling is perhaps one of the most important aspects of overclocking. As you increase your voltages and bus speeds like a mad ox, your heat output also increases. You must balance this with improved cooling, or you could face the consequences... The consequences can be anything from instability, to a completely dead CPU, so cooling is not something you want to overlook.

Passive Aircooling:

"What is Passive Aircooling?"
Passive aircooling is the use of a heatsink to radiate heat from a silicon chip to the air. This helps keep the silicon chip at an operational temperature that it will be stable at.

"What is a heatsink?"
A heatsink is a specially shaped piece of metal, with a base and fins, designed so that the fins can provide the maximum possible surface area for heat dissipation. Heatsinks are manufactured normally using either aluminium or copper, or an aluminium/copper combination. Heat transfers from the chip it is mounted on and into the heatsink, the heatsink radiates and warms the air around its fins. Convection (eg Heat Rises) then deals with the removal of the heat from around the heatsink's fins.

"Where am I likely to see Passive Aircooling?"
You can find passive aircooling in the form of Northbridge/Southbridge chipsets, passively cooled video card GPU's, and even on some modern CPU's (Via C3, Transmeta Crusoe)

"What are the advantages of Passive Aircooling?"
It's cheap and it's quiet.

"Can I passively cool my CPU?"
If your CPU is manufactured by Intel or AMD, then the answer is no.

"Can I apply passive cooling methods to anything in my computer?"
Yes you can. Perhaps the most relevant application of passive cooling within your PC would be the addition of a small heatsink to your SouthBridge, and the addition of smaller heatsinks to the MOSFETs on your motherboard.


mosfets are typically found near the ATX connector

While not necessary if you are running your components at a stock speed, passively cooling these components can improve stability, especially when overclocked.

[whetu]

Active Aircooling:

"What is active aircooling?"
Active aircooling (henceforth "aircooling") involves mounting a heatsink on top of your cpu. On top of the heatsink resides a fan, which can be of any different size, speed, and noise available.

Heat transfers from the CPU and into the heatsink, the heatsink radiates and warms the air around its fins. The fan's job is to either blow colder air over the fins so that the warm air is dissipated, or to suck the warm air off the fins so that cooler air can replace it.

The heatsink and fan combination is normally referred to as an HSF, or more crudely and inaccurately, a "cpu fan."

"What's the difference between Passive and Active Aircooling?"
The use of the fan on the heatsink in Active Aircooling is what defines the difference between Passive and Active aircooling.

"Why would I want to aircool?"
Because aircooling is cheap and commonplace. It is currently the standard cooling method used.

"How do I change my heatsink?"
This depends on the heatsink, however if you are installing a new heatsink, your new heatsink could possibly have some provided instructions (again dependant on the heatsink; $100 HSF's will have instructions, $10 HSF's most likely wont.) If there are some provided instructions, FOLLOW THEM. Otherwise, read on.

The standard attachment method is to clip onto socket lugs, normally using only the middle two of the provided six lugs.

Here you can see a standard cpu socket, with the 6 lugs and socket step outlined. What you want to do is look for the middle lug at the step end of the socket.

Once located (and with your computer off), give a bit of downwards force on the clip, and flick it out from under the lug, and then releasing the downwards force allowing the clip to come free.

This image shows how you want the clip to be at this stage; free of the lug. Be warned though, some clips are worse than others and you may require the use of a tool such as a flathead screwdriver or needle-nose pliers to assist you in the removal of your heatsink.

Now gently rock the heatsink back towards the side that is still clipped. The clip should pop free fairly easily allowing you to remove the HSF completely. Clean up any mess on your cpu using paper towels and meths or cleaning alcohol. Apply a fresh coat of heat transfer compound (Arctic Silver III is a favourite) and continue to install your new HSF.

Installation is very straightforward, in fact just the reverse of the removal method I have just described. Make sure the socket step and the HSF step are aligned correctly, lean the heatsink back towards the side opposite the socket step and slip the clip onto the lug(s). Flatten the heatsink onto the cpu carefully and hold it firmly in place with one hand. With the other hand apply downwards pressure on the socket-step side of the clip and slip it onto the lug(s.)

Double check that the socket step and HSF step are aligned properly, plug in the fan and fire up your computer. Congratulations.

This is a very brief description of the process, and I recommend you do some google searching for other articles before attempting this for the first time. The other thing you can do is get someone who is experienced to show you, there's bound to be an OCNZ member in your hometown, it never hurts to ask! Otherwise, I accept no responsibility for what you may or may not do with your computer as a result of this information.

Take a look here for a more thorough and picturesque how-to.

"What is the best heatsink?"
There are many factors that determine the best heatsink. Aircooling has been engineered to perhaps its optimum performance, so there probably wont be any other spectacular heatsinks coming out.

It is fairly difficult to pronounce the world's best heatsink without having any solid data to back myself up, but generally speaking you can't go wrong with an alpha, zalman or swiftech unit.

I recommend that you read a lot of articles, targetting for heatsink roundups as they will show head to head comparitive results. Here are some good articles:

• * Dansdata's series of reviews
  * The Frostytech series of reviews
  * RadiativeNZ featuring local reviews done by yours truely

"How should I choose a heatsink?"
I'd recommend you give Dans "CPU Cooler Snap Judgement Guide" a read. Keep in mind cost vs performance, read multiple reviews and then make an educated decision.

"How much does aircooling cost?"
Anywhere from free (stock HSF provided with your CPU purchase) and all the way up to NZ$120 and beyond. If you read a few head to head roundups, you'd probably be best to go with a HSF in the $40 - $60 bracket, as they will normally perform within a few degrees of a $120 HSF, thus providing best bang for the buck.

"Are there any risks?"

"Is there any maintenance involved?"
An occasional dusting should be all that's required. The amount you do this depends on how dusty your house is, but once every month or two should suffice.
Every six months or so, I recommend a complete removal of the HSF. Disassemble the HSF and completely clean it. Put a few drops of some fine machine oil into the fan hub (peel back the fan sticker to discover .) Clean off your CPU and reapply some fresh heat transfer compound. Reinstall your HSF and enjoy.

[whetu]

Watercooling:

"What is watercooling?"
Watercooling is the usage of water in a closed system of tubes to cool your CPU. A pump keeps the water flowing through the system, a radiator transfers the heat to air thus making the water cold again, and a waterblock is mounted atop your cpu for the water to pickup the cpu's heat as it passes by.

The advantages of watercooling are that it is quiet, and if setup right, it can far outperform aircooling. As a reference, the best temperatures I've seen in my experience with watercooling was 10c above ambient, with full load on the cpu. Certainly not temperatures to be sniffed at considering the level of silence that comes hand in hand with watercooling.

Heat is transferred from the CPU to a waterblock. Water runs through the waterblock, and heat is transferred into the water. Somewhere along the lines, the now heated water will enter a radiator where heat is transferred from the radiator to air. The now cooled water then continues the cycle through a waterpump which keeps the water moving through the system. The cycle repeats.

"Why would I want to watercool?"
Most PC Enthusiasts switch to watercooling in the search for lower temperatures and a quieter computer. While these are not the only reasons one would watercool their PC, they would be the primary reasons.

"But it's water inside my computer! That's bad right???"
Not necessarily. Given thought and precaution, you can reduce the possibility of anything going wrong. Water in its purest form is NOT a conductor, it is an insulator, so by using de-ionised water, and hoseclamps, you can reduce almost all chance of disaster.

A well planned watercooling rig has about as much chance of disaster happening as your average aircooled rig. The waterblock could fall off, damaging your video card and allowing your CPU to die in a ball of smoke. So what? Your boring, noisy, poor-performance heatsink and fan has just as much chance of doing the same.

This is the biggest hurdle for anyone considering watercooling; the psych factor. You will always have a sub-concious thought in the back of your mind telling you "water and electronics bad, BAD KARMA!!!". It is up to you to decide whether you can face reality and go through with it, or whether you will back off and stick with your heatsink and fan.

We still respect your decision either way

"What do I need to watercool my gear?"

• * A waterblock
  * A waterpump
  * A radiator
  * Applicable tubing
  * Water and optional additives
  * A resevoir (optional)
  * GPU/Chipset block(optional)

With watercooling you should really set yourself a target amount to spend. For me, after a VERY generous $250 you really start to get diminishing returns. Most of that $250 should be spent on the waterblock and the pump. (LiquidCC + Eheim are my recommendation) With these two components its a "you get what you pay for" situation. Skimp and it'll show in the results. Also skimping on components opens you up to a higher chance of something going wrong.

Waterblock:


The waterblock is where a lot of the action happens. It is where the primary heat transfer takes place, and is responsible for direct cooling of your CPU.

While the waterblock is an important part of any cooling loop, it is useless if paired with poorly matched components. A weak pump or a poorly designed radiator can ruin a cooling loop's performance, as can a substandard waterblock. It is up to you to find a balanced combination.

Waterpump:


Perhaps the component you should pay the most attention to is your waterpump. Make sure you purchase a good quality pump if you intend to install your watercooling once and never touch it for 6 months or an even longer period.

The general consensus amongst the overclocking community is that the best pumps your money can buy are Eheim (pronounced "air-hyme"). For beginners, the 1048 is perhaps the best model.

Another popular pump amongst the overclocking community is the Rio 600.

For a shorter period of time, you could use a cheaper pump, but you must realise that cheaper pumps will perform worse, and are most likely not designed for constant operation. Consider the waterpump as the heart of your watercooling system... If it stops, something could die.

Radiator:


The radiator's task is to transfer heat to the air, usually with the assistance of a large slow moving fan.

Rad's can be got for as low as $20 bucks at the wreckers or $175+ for a Blackice... its up to you. The one from the wreckers will need a little work to tidy it up, but thats no hard task. It may also need a little work on the barbs etc, but again not a hard task for someone with basic DIY abilities

Tubing:


Tubing can be of many varieties. You can get vinyl, silicon, tygon, metal reinforced... any number of different types. The type you should go for depends on how much room you have in your case. If you dont have much space, you should consider a more expensive silicon or tygon solution (as they will be more flexible). If space is not a problem, then your average vinyl tubing can be picked up relatively cheaply at your local hardware or plastics stores.

The tubing can be as cheap as 10 bucks, but if you can afford it - definately go for some silicone. Tygon is back into diminishing returns territory and the thin walls make it difficult to clamp/seal every join. If you really have the money and want tidiness/minimal tubing, then go for some clearflex. So basically Silicone or Clearflex. Avoid Tygon.

Water and optional additives:


Many people will use your average everyday tap water. This is not really advisable due to the impurities of tap water, which can promote scale buildups or even algae growth within your cooling loop, which could damage your components and reduce the cooling capability of your loop. Bottled water, preferably of the distilled variety, is far better to use.

There are a couple of household items that you can add. A couple of drops of dishwashing liquid will help the water flow around easier. A couple of drops of bleach will help keep the nasties at bay. Foodcolouring or dyes can give the water an impressive colour that will show up through the tubing, toilet sanitary cakes can do this as well, and keep your nasties at bay - 2 birds with one stone .

There are other items you may want to consider adding such as antifreeze (if you are using peltiers or chilling the water.) Also, if you can afford it, some water wetter, however the dishwashing liquid does pretty much the same job for pennies.

If you are concerned about water leakage, than you can improve your chances of avoiding disaster by using Distilled or De-Ionised Water. Distilled water will also reduce your chances of scale and other bad things forming in your system.

Reservoir:

I personally prefer having a watertight reservoir in my system to help with topping up/bleeding. Closed loop systems are a real pain in the arse to fill/bleed in comparison, and definately not what someone new to h20 needs to go through. You can buy reservoirs for quite a cost (chances are you'll have to import) or you can whip one together out of a click clack, some barbs and some silicone for ~$10 to $20...

GPU/Chipset block:



"How much does it cost?"
As an example for a Purchased Kit: NZ$414.21 (converted from AUS dollars)

Self build as an example
*waterblock - liquidcc surge $90 StylesPC
*pump - eheim 1046 $110 StylesPC
*rad - suzuki van heatercore (PERFECT RAD) $20 local car wreckers
*tubing - depends which type you get, but bog standard vinyl tubing should be no more than $12 bucks all up
*reservoir - depends if you want/need one but a click clack lunchbox does a bang up job, is watertight, and is cheap. top price about $13 bucks for a large box
total: NZ$246
(this is being VERY generous as you can cut a lot of corners and can and will stumble across a good deal here and there, most of the money goes on the two most important parts: the waterblock and waterpump)

[whetu]

"Ok, closed loop or open loop?"
A closed loop is a watercooling loop that has no reservoir, and at most will have a fill tube (a tube used for topping up coolant). Closed loops are usually more difficult to setup and bleed (bleeding is the method of removing air bubbles from the system). Closed loop systems are usually more difficult to maintain as well, so with all these factors in mind, I'd recommend you start off with an open loop.

"What is better - a retail kit or a self-built kit?"
For a beginner, a retail kit is better as each component is designed to work with the other components in the kit. Added to that some (hopefully) well written installation instructions, a retail kit should be quick and painless to setup.

For an enthusiast, a self-built kit is better, as the enthusiast can research each component, hand pick each component, and then build their own kit. They know every niggle with their kit, and they know their kit inside out and back to front. If they were keen enough, and had the resources, they could build some of the components themselves.

Cost is the other factor that comes into discussion. A retail kit is normally specifically designed for use within the confines of a PC Case, a self-built kit can be thrown together out of a well priced waterblock, a garden fountain waterpump, and an automobile oil radiator or heatercore. The self built kit would be many, MANY times cheaper. This is the other reason most overclockers will have a self-built kit: they want to save costs by purchasing slower cpu's and overclocking them, they will also save costs by self-building their own watercooling kit.

"How do I go about setting up my watercooling?"

"Ok, are there any other risks?"
Waterleaks can happen. Pumps can fail. Basically if you design it right, your watercooling system will have just as much chance of failure as the noisy aircooling solution you were using. Disasters can be prevented, and disasters can be got over.

"Is there any maintenance involved?"
The radiator will require the occasional dust, and once every few months you should remove your loop, give it a good clean out and reapply some thermal compound and use a fresh supply of coolant.

Recommended reading:

• * The overclockers.com series of articles
  * An excellent guide by Bravo (This may require registering at the OCAU forums)
  * Zero Fan ZoneThe chronicles of Bladerunner himself
  * Subzerotech's how-to
  * Nordic Hardware's h20 for beginners

Supercooling:

"What is supercooling?"
Supercooling is at present the domain of the crazy, the determined, or those with an actual need for it.

Supercooling is the usage of chemical methods to put extreme cold onto your CPU, normally done through the use of a refrigeration compressor, but often done with Dry Ice or Liquid Nitrogen. Peltiers are probably the most popular method of Supercooling as they are relatively cheap and longer lasting than other Supercooling methods.

"Do I need it?"
If you need to do it, you'll know. Otherwise avoid it.

"How much does it cost?"
One of the problems with supercooling is it can often be dangerous to either your physical self, or your health. Have you seen Terminator 2 where the T-1000 is frozen and then smashes... Do you want that to happen to you? Didn't think so.

Because of this, supercooling is usually expensive, as you have to pay big bucks to get the chemicals you require, and sometimes big bucks to get professional help. Suffice to say that Supercooling can be as ghetto/dangerous/cheap as you want, or as professional/reasonably safe/expensive as you want.

$1000-$1500 is an expected price for a professional supercooling system.

"Ok, I'm game, how do I do it?"
Use the Googlor to search for other articles on supercooling. Read up as much as you can, and when you are better educated, give it a shot.

Good luck.

[whetu]

Case Cooling:

General Notes:

The Importance of Thermal Compound
Mird-OC wrote
Thermal compound should always be used, you can get away without using any compound but temps will be at least 6 degrees higher. The main reason being that to create an efficient thermal junction between CPU and heatsink/waterblock, both surfaces need to be as flat as possible - thermal compound just fills in all the nooks and crannies on a microscopic scale. The difference between the different brands of compounds are minimal (they all pretty much perform within a degree or two - well within the margin of error).

There are basically three types of thermal transfer materials for use with heatsink:

Thermal Interface Material (TIM) - A pad usually found attached to the bottom of new heatsink.
Contrary to popular opinion, modern TIMs are actually very good at what they do. The type of TIMs used a few years ago when processors started to require "advanced" cooling solutions were really very poor quality, although at the time it didn't matter very much. Modern TIMs are quite different and do work very well, but need to be "baked" or "cooked" before they reach their best, so a freshly applied heatsink with TIM will seem to perform quite badly. The other problem is a TIM is a one time solution - once you remove your heatsink the TIM is stuffed, and they leave behind a bit of a gooey mess which is always fun to clean up.

Thermal Paste - An opaque paste, usually white in colour.
Most generic thermal pastes perform quite well, although they have a tendancy to dry out. this attribute is what separates thermal paste from thermal grease (see below). Generic paste often performs worse than a TIM but is easily applied and removed.

Thermal Grease - Thermal grease is very similar to thermal paste except it is in a grease formula which is designed to prevent it drying out. Thermal grease also often contains a metal component to aid in thermal transfer, although the actual difference in performance is minimal (perhaps a degree or two lower than a TIM or thermal paste). Because of these reasons thermal grease is also usually significantly more expensive than thermal paste.

As i said earlier you can actually go without any thermal compound at all, but the idea is to maximise the thermal junction between the heatsink and CPU, and pretty much any thermal compound is better than nothing (even vegemite and toothpaste apparently).

"How do I apply Heat Transfer Compound?"
Look here for my application method.

"What's a shim?"
A shim is a thin piece of metal that goes between your CPU's package and your heat transfer device (heatsink, waterblock etc.) The point of the shim is to protect the core of your CPU from damage from highly pressured heatsinks/waterblocks, or from poor installation of heatsinks/waterblocks.

"Do I need one?"
This is up to you to decide, but personally I have always used a shim since having seen a friend destroy his duron simply by putting it in a car and taking it to work. The case flex (and his was a half decent case) added to the tremendous downwards force put on by his HSF was enough to crack his CPU. A shim is a cheap investment to protect possibly an expensive investment. I'd rather spend 20 bucks for extra piece of mind for my 200 dollar CPU than take the risk...


"Does the shim help cooling at all?"
This is a very debatable topic, some claim that a shims' only purpose is for protection of a CPU core, some claim that it also has added cooling benefits by increasing the surface area that the heatsink base comes in contact with. My opinion is no, it does not help cooling, and if it does, the difference will be so miniscule that it will be within the margin of error of your temperature detection.

"Ok, you talk about temperatures, how can I find out mine?"
This is a bit of a grey area. The problem with most motherboards is that they use an external temperature sensor, so any temperatures you read won't really be the true temperature of your cpu. So you can't compare your temperature with your friend's. You have to compare apples with apples. If your friend has exactly the same motherboard and cpu, then you can compare. If you have say, an ASUS mobo, and your friend has an Epox, you can't directly compare, as your temps are most likely measured differently and will have other affecting factors such as other components used and the case used.

Intel CPU's have used built-in temperature diodes for awhile now, so their reported temperatures are reasonably accurate. AMD has only implemented built-in diodes a few CPU generations ago, but the issue here is that being able to read them is motherboard dependant. While many AMD motherboards can now read from the built in diodes, there is still an alarming number that can't.

Next time you change your heatsink, pop your CPU out of its socket and have a look underneath. If you see a small smokey-coloured plastic strip, then you have a Thermal Probe. If you have a small (normally) blue onion-shaped component, then you have a Thermal Diode.


A typical thermal probe


A typical thermal diode

*Thermal Probes are normally accurate to +/- 3c
*Thermal Diodes are normally accurate to +/-10c

So dependant on what you have, take your readings and just consider it's true accuracy. If you are reading from a built-in diode, don't worry, your readings are accurate .

Now, to read your temperatures, try the following links:

• * Motherboard Monitor
  * link here
  * link here

"Okay, I'm not reading from a built-in diode. Can I get a more accurate reading?"
Sure, you can purchase a Senfu Thermal Probe and put it in direct contact with the side of your CPU core. If your CPU does have a built-in diode, you can modify your motherboard to read from it, however you should be aware that in doing so, you will void your warranty. Look here, and here to learn more.

"What temperatures should I be aiming for?"
Generally the colder the better. Chances are, the reading you take will be an idle reading, to see the upper limits of your current cooling, put some load onto your cpu with a load program such as prime95, CPUBurn, or a distributed computing program such as setiathome. No matter your CPU, be it Intel or AMD, a good temperature to aim under is 45-50 degrees centigrade with full load on your cpu.

"My temperatures are awfully hot! What can I do???"

Lapping:
Gideontech's Heatsink Lapping Guide

Other Articles:

• * The Procooling.com series of articles
  * The OCNZ article listing
  * Overclocked CPU Wattage Calculator
  * Tech-PC UK's excellent article
  * OCAU's Extreme cooling thread
  * Motherboard Monitor
  * Atomicmpc forums "Temperatures Explained"

[whetu]

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