WhiskeySix

Introduction

I use a Dell Inspiron E1705 with a Nvidia GeForce Go 7800 video card. This is a great card, but it generates a LOT of heat in a laptop. For this reason (to reduce heat production) Dell ships the card underclocked with a core clock of 250MHz (down from almost 400MHz in the desktop version of the card). With stock Dell cooling, the card would idle in the ~60°C range and max out at almost 80°C under load. Once I realized this, I decided some auxiliary cooling was in order.

I tried a Bytec laptop cooler, but was quite disappointed. The problem with it, as with most generic laptop coolers, is that it just blows air around the base of the laptop. What I wanted was something to blow cool air into the intakes for each fan. The GPU and CPU fans are located towards the back of the laptop, with the GPU being on the right side and CPU on the left (when right-side-up). The both are centrifugal fans that pull air in from above and below and blow it out the back of the laptop:



So to increase the air-flow, I decided to implement something like a cold-air and/or ram-air intake on a car. I did this using a 120mm fan to blow air through 3" PVC routed directly to the intakes:



With around $40 in parts, I was able to increase my GPU clock speed by almost 50% to over 370MHz!! What follows is directions on how do create this cooler yourself. If you're having heat problems with your laptop or want to explore overclocking*, give it a try!

What you will need

• (1x) 120mm fan - I highly recommend the 9-bladed Sliverstone FM121. It comes with a fan-speed control knob included, has variable output between 38CFM and 110CFM (plus it's all white)
• (1x) 3" x 24" PVC Pipe - HomeDepot sells PVC pipe in 2 foot lengths for a few dollars
• (2x) 3" PVC "T-Hub" connectors - These have a short rise on the perpendicular branch of the split.
• (1x) 4"-to-3" 90° connector
• (1x) 12v, 0.5A DC Power Supply - I happened to have a few of these lying around, but you can get them cheap at any RadioShack. (The connector on the end doesn't matter because we'll end up cutting it off anyway)
• (1x) Plastic Shopping Bag
• (12x) 4" zipties (white)
• Wire cutters
• Drill with a various sized bits
• Pliers
• Non-conductive tape
  

Step 1: Mount the Fan

The first thing to do is lay the 4"-3" bend piece on it's side. In addition to holding the fan, the 90° bend works like a kick-stand to keep the base flat. Center the fan on the opening and drill four holes into the to the sides of the opening. From the inside, insert a ziptie into each hole so that the 'nut' of the ziptie is inside. After checking to verify that the output of the fan will blow into the tube, run the 'pointy end' of each ziptie through the mounting hole and attach the 'nut' from another ziptie. The tie's I was using weren't holding well, so I ended up using two for each corner:

Step 2: Connect the Power Supply

- Drill a hole in the inside-bend of the 4"-3" bend pipe.
- Cut the tip off of your [unplugged] DC Power Supply, and then run the wire through the hole.
- Cut the adapter off of the power-wire for the fan and splice it together with the supply wire. (red to red, black to black, then wrap with electrical tape.)
- Tie a simple knot in the end of the joined wire to prevent it from coming back out through the hole we just drilled.

Step 3: Install the Fan Controller

This SilverStone fan is variable speed and comes with a nifty little knob controller. The first thing to do is to remove the knob from it's panel - once you pop the knob off, there's a nut holding the actual controller in place. This will likely require pliers or a wrench to remove.




Next, you'll need to drill a hole in the outer wall, opposite the power-supply hole. You'll need to move the drill around in order to flair the hole enough so that the nut gets a bite on the threads the outside of the tube:




Once you have the knob installed, you need to deal with the wire. The fan-kit allows for the knob to be 3ft. from the fan, but here it's only a few inches so there's a lot of extra wire. You can either gather and tape it to the side as shown above, or just cut out the middle portion of the wire and splice it back together (which is what I did).

Step 4: Prepare the Base

Now we're ready to start building the PVC base. First thing to do is measure and cut the 3"x24" pipe to fit your laptop. As shown above, you want the outside of the exhaust ports to be over (under really) the intakes of your laptop. (be sure to account for the overlap between T-Hubs and pipe when before cutting. Once you have the center pipe cut to length, connect all three pieces, and level them (put them face down on the table so that the openings are on the same plane):

Step 5: Plug end of the Base

There's a million different ways one could do this, but I decided to use a white plastic shopping bag wrapped over a small scrap of PVC... works like a drum head, and forces all 110CFM of air up towards the laptop.

Step 6: Orient the Base

Before connecting the fan, the base must be placed under the laptop to establish the proper angle.



In this configuration, the base has a tendency to roll forward or back. This rolling will be stopped once we attach the 90° fan connector.

Step 7: Connect the Fan Assembly

Once the Laptop is stable on top of the base, slide on the Fan Assembly. This will act like an outrigger to balance the whole system:

Step 8: Enjoy your new cool laptop!

(My desk is a little cramped, so I ended up pointing the fan shroud down towards the floor - as you can see in the photo on the left. This did make the base a little less stable than when it was on the desk, but this was solved using a couple of pieces of foam to give the front of the laptop some traction)

Notes:

• The pressure is so high when it's at full blast that it overwhelms the built-in fans - air actually blows out the side and top intakes for each fan. To mitigate this, I just added some scotch tape over those inlets so that all the flow is redirected over the heatsink in by the rear exhaust port.
• The PVC should fit together well enough that no adhesive is necessary
• If you don't have CPU heating problems, the end-plug barrier (shopping bag in this instance) can be placed between the T-Hubs, so that ALL of the air goes to the GPU heatsink)

Results:

As I mentioned above, this mod let me increase my videocard speed from 250MHz to over 370MHz. Not only that but my max temperature actually dropped under load. At 250 MHz, without the cooler, the GPU temperature peaked at nearly 80°C. At 370MHz, with the cooler, I peak at 68°C!

In game (BF2), this clock boost translated linearly to almost a 50% increase in average frame rate. Using FRAPS to log my framerate every few seconds, I saw my average increase from ~50FPS to around 75FPS!

*blah, blah blah, everything you do, you do at your own risk

[digg it?]

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Reflexes are for mistakes only. Reaction implies surprise. Be surprised less.

Wimpinator

Brilliant!

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|TG-6th|Wimpinator

sc1ence

very cool. Literally, and figuratively.

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__3rd SFD__

jackmacokc

Sweet whiskey..nicely done. Strangely I found a link to this on Hack A Day http://www.hackaday.com/2007/05/20/f...aptop-cooling/

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Apophis

Dugg! It also made it to the front page of hackaday.com. Oops. Jack beat me to it!

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Diplomacy is the art of saying "good doggie" while looking for a bigger stick.

WhiskeySix

"sure, it's not pretty" pffff... puhlease. White's the new plaid.

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Reflexes are for mistakes only. Reaction implies surprise. Be surprised less.

Apophis

Insane.. Over 2500 thread views since this was posted.

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Diplomacy is the art of saying "good doggie" while looking for a bigger stick.

flux

An here I thought I was special with my Toilet PVC mod. Nice work!

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flux
[tg-c1]

WhiskeySix

^^^


After some more experimentation, I'm definitely no longer temperature-limited. I can run the GPU at any speed and get the same peak temps (67-69°C). Now I'm just speed-path limited by the GPU die itself. I can run at 379MHz, but 380MHz fails the nVidia control-panel's built-in test. nVidia must have binned some lower performing GPU's for use by Dell since they knew they'd be underclocking... looks like 'standard' 7800's are supposed to run at 400MHz.

I've also found a sweet spot for the fan-speed. Not sure what RPM's it's running at, but cranking it up to leaf-blower mode isn't necessary

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Reflexes are for mistakes only. Reaction implies surprise. Be surprised less.

Dick Blonov

I love it!

Great plumbing job

DB

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|TG-6th|Blonov

loyalguard

That is awesome Whiskey! PVC...it's not just for plumbers and sk8ters!

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|TG| LoyalGuard

jmaker

You are brilliant my friend!

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tetsuo001100

love the portability of it m8. interestingly enough i've been doing something similar by just putting my laptop over the AC vent! LOL. will definitely be heading to the homedepot.

Fighter

lolz. That is actually a good idea. Absolutely brilliant and very resourceful Whiskey, you should appear on GMA for a technology segment.(with Bamboo of course )

=DdogG=

wow - Zombies walk among us....

I thought Halloween was over.

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Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -Albert Einstein
The two most common elements in the universe are Hydrogen and stupidity. -Harlan Ellison

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