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G5 mod - CLEAN - airflow question

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Hey guys.


Im currently working on my G5 mod and just completed the hard part - I have cut the rear and placed my tray in it by using the original G5 fan mesh. It looks clean to me, I will post pictures when the raw construction is over. I have ordered some fans and the PSU yesterday and I'm not sure about the airflow that I want... I have two ideas and would be very happy if you could guide me to the best alternative:


1: From bottom to top




This design is all about positive air pressure. All fans are intake, which means that the amount of dust entering the case is more control able, isn't it? Heat is also rising and I hope the airflow will benefit from this design... What do you think? Bad idea? Why?


2: From left to right (standard?)




I see this kind of design in almost every G5 mod and there might be a very good reason for that. Is this deign better than my thoughts above? Will the amount of positive air pressure be enough to keep most dust outside?



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I would say because your pulling a lot of air from the ground, the dust filters would clog easily restricting airflow. Your design might work, and it also might lead to an unhappy PSU and GPU (in terms of heat). All that hot air from the CPU (gee, don't you just love acronyms) motherboard and hard drive will go out the front panel or sucked into your PSU and GPU. Depending on how much heat those give off, that might not be the best idea.


If you really just want dust control, pick up some AC vent filters and stick it around all the holes of the chassis :P .

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Hmm, sounds reasonable to me. I just forgot about the main part: temperature. Maybe I'll just do the left to right design. Bottom top would work with good temps if I would add another intake at the left, wouldn't it? But there goes my money again... So I'll probably stick with the standard design. Any other opinion someone?

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Because I design a lot of passively cooled systems, and I work specifically with airflow, I would strongly suggest using air pressure to your advantage.


Negative air pressure in the Mac Pro/G5 cases is a wonderful thing, and works incredibly well.


Don't use any fans in the front, the exhaust fans in the back will pull a more than adequate amount of air through the computer to cool all of the components.


2x 92mm fans will do fine, 1x 120mm or even 1x 140mm would be even better though. Whatever suits your fancy really, but spare yourself, and don't mount fans in the front. Dust buildup will occur much faster with intake fans than relying on negative air pressure, even in the cleanest houses. Don't bother with air filters though, I work in a computer shop, and even the customers who build their own machines and "take really good care of them" don't clean them at all.


Also, please, don't put any fans on the bottom of the case. Utilize Front to Back airflow, and your temps will be perfectly acceptable. Do not worry about keeping the temps within 30C, modern hardware is capable of operating perfectly well beyond 70C for some time. The hard drives will stay very cool with even the slightest breeze, and the GPU will do fine with it's own cooler. Any tower based heat pipe cooler will keep the CPU very cool, and you wont have any problems.


More fans does not mean it will stay cooler or perform any better, so save yourself the trouble of cutting/drilling spots for them where they don't belong. Keep in mind that stock Macs use a front to back airflow pattern using push/pull fan setups to keep fan speeds down, but you're not running a dual socket board, so you aren't pushing the heat from one CPU through the heatsink of the next. If it ain't broke, don't fix it.


The hard drives can go anywhere in the front, but don't interrupt the airflow, you don't want a pocket of heat to form. Air will follow the path of least resistance, so the trick to keeping a computer cool is to control the path of airflow. If you want to ensure the computer will run cooler without changing much, create a duct, don't add another fan. It will do the trick quite well. Plastics lined with a foam on the inside will keep noise under control, increase the pressure of the airflow, and give you lower temps, and the temps will stay lower over time.


Finally, yes, heat rises, but remember that if you control airflow with ducting, as well as picking the right fans (smaller center hubs, higher static pressure, temperature controlled, etc), you wont have to worry about it.


Choose your components wisely, and it'll be a walk in the park. For example, if you want the ATI 6770 GPU, you should look into the MSI Twin Frozr model, as opposed to other reference models because it has a MUCH better stock cooler, and will run a lot cooler right off the bat. Additionally, if you wanted an i7 2600, but you aren't going to overclock, the i7 2600S is a lower wattage model with just as much power, resulting in cooler operation. 30nm Samsung RAM is also an important thing to keep in mind. And finally, no high wattage power supplies. Unless you're running quad-SLI, you really aren't going to need an ounce more than 550W, at best. A high quality 430W or 520W power supply will do much better than a cheap 750/800W power supply. Antec and some other brands are not ranking their power supplies on continuous output rather than peak output, so the Antec HCG-520W power supply peaks out close to 600W, if not more. Component choice will greatly affect the end result of your cooling needs.


So, from me to you, lots of experience later, front to back airflow, and high quality components will do much better than an overblown cooling system, and it'll last a lot longer.


If you need additional help, feel free to ask, I stop by many forums when I have the time.

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Hey, bonestonne. Thanks for your nice explanation but unfortunately I finished the raw construction before I read your reply... I used two 140mm fans in the front and two 92mm fans in the rear. I think I will use them with low rpm... I'll post pictures after finishing the power cord extender (as the PSU is placed in the top section and I want the cable to be plugged in at the bottom). Just need to get the parts and I'm back.


My system will be something like this: 2600k, Gigabyte UD3H-B3, Thermalright Silver Arrow, Gainward GTX 560 TI, 32GB RAM, a 630 WATT PSU from BeQuiet and a SSD and HDD (with place to expand). I hope these parts are of enough quality to get good cooling and good airflow.


Anyways, I'll post pictures in a couple of days.

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The Thermalright Silver Arrow looks like a decent CPU Cooler, I've always had a tendency to stay away from that brand, but the way things are going, everyone is more or less making the same thing.


If you are not going to overclock your CPU, I would strongly suggest using the Core i7 2600S, and as far as the GTX 560 goes, I would look for using the MSI TwinFrozr model, I detailed this in my last post about why, it will reduce the amount of heat and power usage. I also suggest that you really think about the necessity for 32GB of RAM, if you'll be running the Mac OS, that's going to be an insane number. Even the most powerful video editors that I'm familiar with working in never needed more than 16, and this wasn't just for youtube videos, this was for actual TV Production. The reason many of the terminals had stopped at 16GB is because everything was linked together as a Render Farm, so the export process was more "hive minded" and every machine that wasn't in use ended up helping out, so the individual computers were more than enough. Even though RAM is cheap, I'm hard pressed to say more than 16GB is necessary for anything.


BeQuiet makes some absolutely spectacular power supplies, quite the lookers as well. And as a final note, before setting your SSD up, I would strongly suggest reading into the proper setup of SSDs and the partition requirements, as improper setup can cause some serious problems.


Hope that helps you out.

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