Cooling your CPU with dry ice does not sound like a good idea. There are many problems associated with this technique.
1) Dry ice has to be bought, stored, and handled very carefully. It
doesn't last all that long (it sublimates, boiling off carbon dioxide
constantly). You can't touch it with your hands (wear extra-thick
gloves, and keep water away!). You may be able to get some at ice-cream
shops, but the cost may add up to more than $100 if you run your
computer a lot like this.
2) You constantly have to add more dry ice -- it sublimates away
all the time. Depending on the size of the chunk you put in your
computer, you may have to replace it every few minutes. A 2.2 GHz
Pentium 4 (a typical modern processor) dissipates 57 watts of thermal
energy. The latent heat of dry ice is 590000 Joules per kilogram,
meaning you'd go through the stuff at a rate of about a pound an hour.
Overclocking only speeds this up. And it absorbs heat from the air and
surroundings, not just the processor, so it disappears even faster.
3) In a humid environment, the dry ice will frost up. Water vapor
will condense on the block of dry ice and make regular ice. When the
dry ice sublimates, this stuff falls on your processor and motherboard,
making it wet. Even just cooling off the components of the computer
below the dew point will cause water to spontaneously condense on your
computer parts. They may not work when wet (short circuits!), or the
water may speed the corrosion of electrical contacts.
4) You need good thermal contact between your dry ice and the
processor. Dry ice when it changes into a gas, makes a thin cushioning
layer of escaping carbon dioxide around it. This acts as a thermal
blanket, keeping more heat from traveling to the ice. You can push the
dry ice against the CPU, but what will happen then is that you will get
vibrations. Vibrations tend to shake electrical contacts loose.
5) Speaking of electrical contacts, cooling a portion of your
computer down to very low temperatures and not others will create
mechanical stresses in your computer parts (most likely in your
processor). When stuff cools down, it shrinks, and when it heats up, it
expands again. Cooling down only a part of your computer makes that
part too small to fit nicely into the other parts. You may crack
something or, more likely, just break some electrical contact
somewhere. Small electrical components can be fragile!
6) You have to make sure not to run out of dry ice -- if you run
empty, the processor will overheat very rapidly and stop working.
Water cooling is difficult -- you have to make sure there are no
leaks and no vibrations introduced by pumps. It is (was) often used for
large mainframe computers, but is not common on today's smaller units.
Our suggestion is to get a good heat sink and a fan. There is no
limit to how much heat they can carry away -- air comes in for free,
and the fan and heatsink are not that expensive (your computer probably
already came with one, but you might want to get a better one). You may
want to look at heatsink roundups on computer-related websites, but be
forewarned about the quality of information you may find on the web.
You can also slow down the processor again. Usually you can get more
performance out of a computer by buying one later, as processors get
cheaper and faster all the time anyway, and overclocking is just a
really hard way to go about this.
-Jeff and Tom
(republished on 07/25/06)