It’s the Case Stupid……

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Tips on case cooling – Rick Davis

I’m a student of Hard-Knocks University for sure. There wasn’t a course at the local community college on ‘Overclocking PCs’, so like most of you I had to do with help from friends and internet articles. I’d like to share some knowledge dealing with air-cooled systems.

I am fully aware that there are viable alternatives to using fans to blow ambient air around components to keep them from self destructing. Water cooling, chillers and the like are extremely effective and provide means for reaching overclocked performance not possible in most air cooled situations. This article is for those who choose to air-cool – and there are good reasons for doing so.

Many of us tweak our computers for the satisfaction. Most of us do so to squeeze the last possible drop of performance out of our investment. Some will overclock a PC even when it’s not cost effective to do so. (I know some folks who have paid more for a cooler than on a cheaper new processor.)

For me it’s about performance on a realistic budget. That’s why I haven’t used any alternatives to air cooling yet. I always come to the conclusion that the extra money is better spent on things like RAM, CPUs etc. Now that’s not to say I wouldn’t like to have a water cooler – I’m just too darned cheap to buy one. Due to my penny pinching ways, I learned a few tricks along the way.

This article is going to assume a few things first:

  • You already have a motherboard, processor and air cooled devices properly installed. (You did use that thermal paste right?);
  • You are comfortable with making changes to your case and cabling;
  • You have the proper case for the job (the wrong case or a too small case won’t be helped by these tips);
  • You are willing to spend a few bucksm but not as much as for a water cooler, fancy aluminum case or the like.

Just take a look at customer reviews for just about any processor cooler out there. One thing you’ll notice is how many folks counter each other in results. One guy gets his AMD 3800+ to run at 40ºC (we’ll use C because its universal) while another with the same processor and same cooler gets a steamy 55ºC. Why is that? Well, it’s probably the case, or more specifically the arrangement of everything in it.

You have to get the ambient air temps down first!

Everything inside that case is generating heat including the drives, the power supply, CPU, motherboard, chipset and even the fan motors themselves. That means getting the hot air out of the case and fresh air in. That expensive copper contraption strapped to your dual-core isn’t going to be very good at cooling if the air inside the case is already as hot as a Dallas sidewalk. This is probably one of the most common cooling errors made. Now remember we don’t have an unlimited budget and we probably have to make do with what we have lying around – right?

Okay let’s tackle case cooling:

Tip #1: Look at your exhaust fans.

You should have at least two – one for the power supply and at least one for the case. Are they mounted behind a metal plate with punched holes? If so, that perforated area needs to go. It may look open, but case fans have terribly low pressure, and even the tiniest obstruction impedes airflow.

There are two ways to fix this: cut the entire area out with a tool like a Dremel, or drill oversized holes on the plate (no bigger than 3/8″ for safety). Rob a metal fan grill from an old case or buy one for a couple bucks – these are usually chrome and look good to boot.

These flow far better than any perforated plate and offer enough protection to keep most things out of the fan. Just be sure to remove the power supply and all electronics from the case if you cut or drill it. Metal shavings are not your friend! I have done this with tin snips. It is hard to do, ugly and you might bleed in the process. You are lucky if you have a plastic cover – it’s much easier to deal with.

Tip #2: Make sure the air can get in and out.

If all the case fans are blowing out, then air has to get in through cracks, optical drives and such. That’s not good. If you have two case fans, one usually moves air inward and the other outward. The idea is to move the air along.
Check the airflow with some tissue or a careful use of a lighter flame placed near an open card slot. You’ll see if the air is going in or out.

If it does so strongly in either direction, it’s because air is not able to freely flow through the case and you have a pressure imbalance. You want to feel air moving in or out of the case fan(s) vigorously, while at the same time not see much pressure in either direction through the open expansion slot. NOTE: if you only have one case fan, this is not applicable, but if that’s so, then you’re not likely getting enough air moving for any serious setups.

Tip #3: Move those cables out of the way.

Use zip-ties like crazy. Wrap loose bundles of wire to make a tight bundle. Route cabling so it’s flat against the side of the case, or at least as far away from the RAM and CPU cooler as possible. One trick a lot of folks never try is to run the cables behind the motherboard. Some cases don’t have room for this, or your cabling may be too short. Just be sure the cables cannot get cut on case edges or pins sticking out of the mainboard.

Some thin plastic sheeting is perfect to protect wiring that would otherwise touch the sharp pins on the back side of the board (clear report binder covers work great) Use round cables for best airflow if they must hang in view. You should be able to make a fist, and pass your hand between the air inlet and the exhaust passing over the CPU without anything blocking your path.

Tip #4: Make sure the case isn’t enclosed by furniture or pushed too close to walls.

A friend of mine burned up two power supplies before consulting me; as soon as I saw his setup, I knew the problem: He had his computer tower stuck neatly in computer desk shelf. There was nowhere for the hot air to escape to!

Tip #5: Keep it clean!

Even a small amount of dust buildup can lower fan performance. Use that canned air to blow off the dust and vacuum it out gently. If you smoke near your PC, it’s going to get dirty more quickly. Smoke residue even causes fan bearings to gum up and fail. Check fans often. PCs sitting on the floor will suck in more dust and dirt than a table top placement. Some fans come with filter media on them. Just be aware that the filter media itself will may cut airflow considerably.

Tip #6: Always ensure the power supply fans blow outward.

Some designs take outside air and blow it into the case. This makes no sense for most applications, as the air entering the case will be preheated by the power supply. Never rely on a power supply to assist cooling your processor. This was a popular method back in the 90’s when processors would live with only a passive heat sink. Today that’s not going to happen and you’ll only blow hot air on your CPU. If its direction is wrong, just open it up (carefully and while unplugged) and turn the fan around.

Tip #7: Try to keep air flow in a linear path.

In other words, don’t put a fan blowing inward right below the power supply blowing out of the case. This will only cause turbulence inside, and much of the cooler inlet air will go straight into the power supply and not into the case. Instead, try to get air moving into the case from the front or sides and exit at the back and or top/bottom. This forces the cooler air to travel across the components inside, picking up the heat along the way and taking it out.

Tip #8: Move air over passive heatsink.

Video Cards now come with fans, but if you still run a passively cooled card, try to move air across the card. I have dangled a small chipset fan off the end of the card with Zip ties and it worked great. Again, it works best when the air in the case is sufficiently cool.

Tip #9: Get as large a fan as possible for each application.

A 120mm fan has 78% more surface area than a 90mm fan, and as such can move almost twice as much air, often with less noise. If you air cool, your cheapest and best bet is bigger fans (not always faster) in almost any case.

Remember, Cool the case first.

To see what a cooler case will do for you, just remove the case covers and watch CPU temps. If it drops measurably, then your case cooling needs attention. Cool the CPU next. Stock coolers do work, but there are more efficient designs around. Don’t neglect the power supply. These need good airflow too. And don’t fret too much over hard drive heat. Yes there is a limit, but its not nearly as critical as most of the other components in your case.

If you follow these tips, you’ll get a lot out of air cooling. Now if money is no object, get yourself an aluminum case with water cooling. And if money is really not an object.. Buy me one too!

Rick Davis


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