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[ale] quick tips - system cooling, harsh conditions

Hi all,

I've discovered a couple of other tidbits about system building in regards to cooling that I thought I'd share.  Some may know these things.  Others may not.  Hopefully, it will be helpful.

I'm running this system hard, using multiple gpu's for computations.  I'm pulling 450+ W from the wall outlet.  I want the system to stay cool enough and not fry to death.  Many people get obsessed with quiet.  However, pulling this much power through the unit, I can't afford to be worried about quiet.  I have to keep lots of air moving.

I'm a fan of Antec cases, although I would buy others if they had the features and price I wanted.  For this build, I have a big full tower case with 9 slots on the back panel.  In terms of cooling, it has an air intake on the bottom (which won't work sitting on my living room carpet) and 2 in the front.  From the factory, it had 120 mm exhaust fans, 2 on the top, and 1 in the rear.

Here are my tips if you're going to be pushing your system to the limit.

Tip 1 - Make sure the case has screens on every intake.

These should be a fine mesh 2-4x smaller than window screen wire.  Any dust that gets through is subject to deposit itself on fan blades and heat sink fins.  Don't ask me how I know.  OK, I'll tell you.  My house is dusty and I've seen the dust totally clog heat sinks.  Best not to let it into the system at all.  Clean or check the screens often.  This case already has removable intake screens.  Also check and clean heat sink fins that are accessible.

Tip 2 - Add fans.

This case had front intakes, not fans.  This is common.  Since I knew cooling would be an issue, I went ahead and added 2 120 mm intake fans in the front.  I'm also a fan of the Corsair brand.  For high air flow with reasonable noise levels, I recommend a Corsair AF 120 mm or AF 140 mm PERFORMANCE edition.  They have a quiet edition with less airflow and rotor speed, but that's not what I want here.  I want lots of air moving.

So, at this point, I had 2 new intake fans and 3 stock exhaust fans.  I thought that would be enough.  Actually, I had already replaced the rear exhaust fan with the dual Corsair fans attached to the liquid cpu cooler.  So, the rear exhaust port might already have more airflow than standard.

I fired up Mint and the 3 gpu's and watched the temperatures.  As I mentioned before in another thread, when you stack up multiple gpu's, all but the last one will have its fan (on the side) obscured by its adjacent cards.  The operating temperatures of all cards, except the last one with the open fan, will be substantially above normal.

I monitored the temperatures, and found the two obscured cards hovering around 88 deg C.  That worried me.  I've read cards can be damaged in the 90 - 100 deg C range.

I felt around the outside of the case.  The airflow from the liquid cooling radiator seemed OK.  However, the air flow from the top fans (provided by Antec built into the case) was barely perceivable at all.  Note that I had already added 2 high performance intake fans and had replaced the rear fan to install the liquid cooling system.  Note also, that in non severe operating conditions, the factory fans might be fine.

So, I decided to replace the remaining 2 top exhaust fans with Corsair high performance fans as well, and went to Fry's to get them.  I returned and installed them.  So, at this point, I have 2 high performance intake fans, 2 high performance exhaust fans, and dual exhaust fans (provided by Corsair with the radiator) working in tandem pulling exhaust air through the liquid cooling radiator.

I fired the unit up to see what would happen.  I ramped the 3 gpu's up to full load doing calculations.  I was amazed at the difference.  The hottest gpu is now at 77 deg C under full load - a full 11 deg difference.  I can deal with 77 deg much better than 88, and I think the card can too.  The other two cards are at 74 and 65.  I should be able to run this for quite a while at full power.

So ...

Tip 3 - Replace the case fans, unless they're designed for high air flow and severe duty already.

Here's an interesting tidbit.  The computer is now quieter, and is pulling 15 watts less - probably since the gpu fans are not screaming their blades off.

Tip 4 - Monitor all the critical temperatures.  I'm monitoring 3 gpu's, the cpu, and 2 hard drives.  I'm not using automation, just looking at the readings, but you certainly use automatic alarms and utilities.

Tip 5 - May be self evident, but, if you're running right at the limits, if any fans fail, or any parts start acting abnormal, shut the system down immediately.  If something goes wrong, you could get thermal runaway on the components very quickly.  Even though they should self throttle, this may not be very graceful, and the system could still be damaged.

Hope you find this helpful.




Sent from my Android Acer A500 tablet with bluetooth keyboard and K-9 Mail.
Please excuse my potential brevity if I'm typing on the touch screen.

(PS - If you email me and don't get a quick response, you might want to
call on the phone.  I get about 300 emails per day from alternate energy
mailing lists and such.  I don't always see new email messages very quickly.)

Ron Frazier
770-205-9422 (O)   Leave a message.
linuxdude AT techstarship.com
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