Cool Computer Case

This was originally my main computer, but Saadia has sinced inherited it as I replaced it.  That gave me the opportunity to hack up another computer case (see CoolCase2).  While I was planning to upgrade this machine to K6-2 (Sep 98), I thought about how I would control the heat that develops in CPU cases these days.  I saw a bunch of good ideas from the various fellow inventive computer enthusiasts on the web and came up with something of my own.  [note: I was delving into this long before the current computer cooling fad --I even put one of my 120VAC 120mm fans on top of my stereo receiver long ago; its lead goes to the switched receptacle on the back so it turns on with the amp]  On with the show:

The goal most of tweakers pursue is simple:  Cool the CPU (and, likely, the video card) and remove the heated air from the case.  The computer will be more reliable and last much longer.  This is also necessary for anyone wishing to push their system components beyond original specs.

The latest generations of CPUs, video cards, HDDs and other internal components produce a lot of heat inside the case.  CPUs usually come standard with a heatsink/fan combo and heatsinks are showing up on video cards more often.  Everyone knows a lot of heat comes off of these heatsinks... but often, that heat is not allowed to escape adequately from inside the CPU case.  You need good quality heatsink/fan combos, but the effectiveness of the heatsinks are limited by the air temperature around them.  For example, when the computer is first turned on, the inside of the case is at room temperature.  The heatsinks dissipate the heat to the surrounding air (more effectively if there is a fan on the heatsink).  Now the air temperature inside the case increases.  Most power supplies have a fan that usually exhausts heat from the power supply and pulls that air from inside the case.  This helps the case temperature a little, but is not adequate for modern CPUs (hey OEMs, are you listening?!?!).  Some cases have another fan somewhere, maybe on the bottom behind the face plate intaking fresh air and/or on the rear between the middle and top exhausting warm air.  This takes advantage of the natural rise of heated air.  With reasonable room temperature, extra case ventillation is more than adequate for most computers.  But I could not be normal.  I had to cut more holes.

With the seeds of an idea, I scrounged around through my pack-rat piles.  I had three spare 120mm 120VAC fans, one of which had a switch and switched outlet built in to its enclosure.  The fans ran rather quiet (especially with an air filter over the intake side) and I decided to over-engineer the project and put all three fans on the case (MORE POWER!).  An advantage of these AC fans is very high air flow without taxing the power supply (and maybe reduce line noise to the P/S).  Also, I can set the direction the fans blow --I chose to intake fresh air through the filter and keep the dust down inside (besides moisture, heat and electro-static discharge, dust is another big enemy of electronics).

I took the case cover off and placed the fans so that they would blow over the video card and CPU.  I then used a Sharpie marker to trace the main holes and screw holes.  A coffee can was the perfect length to place between the sides of the case cover to keep it stable while I worked.  I drilled the screw holes and starter holes for the jigsaw.  I finished/deburred the holes with a wire brush (on a drill or die grinder) and a round file and used appropriate-length #8 bolts to secure the fans to the outside of the case with the guards on the inside of the case (gotta keep the cables from hitting the blades).  I know it sounds kind of bulky, but using the right length of bolts minimizes the difficulties of removing the cover.  Honestly, I have no problems removing the case and the case easily stands up alone without tipping over.

Picture: looking through the fan holes. | Picture: running fans.

It is important to route the cables and secure them (using ribbon clips and cable ties) so that everything is neat and air can flow to the critical areas.  Anyway, using rubber bands, I covered the fans with air filter material left over from one of those cut-to-fit air-conditioning filters (pack-rat comes through again!).  Given the environment, the filters get dirty very quickly... I need to invest in one of those ionizing air purifiers.  The huge volume of air needs places to go so I drilled lots of holes in the spare 3.5" face plate (the HDD sits right below this... perfect!), drilled out the 12 x 7 array of cosmetic dimples on the bottom half of the face plate to 1/4", and removed the card slot cover for the card slot right below the video card to get rid of heat from the G200's heatsink.

[Feb 2000] In retrospect, I did not need the huge volume of air.  When I upgraded my main workstation to a K6-III, my wife got the the K6-2 with the mobo and memory.  I removed all but one of the 120mm AC fans on that case and added a high-flow Sunon 80mm intaking the front, blowing right over the CPU and its HSF.  One additional word, I have seen some folks leave the case cover off... great idea except for one very important fact: the computer case (including the case cover) prevents Radio Frequency Interference (RFI) between the computer and its environment and vice-versa.  I have heard arguments that the RFI is negligible but, having an understanding of RFI (B.S. in EE, Electrical Engr for the USAF) and a practical mind, I proved the RFI can be significant with some observations.  Conclusion: leave the cover on; the case has an FCC certification for a reason.