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Coolers
How do you tell a good heatsink from a poor one, and, more importantly, what makes a
heatsink work? Is it the material used, the way it is built, or simply how powerful its fans
are? These questions come up quite often; people ask if they should spend that extra cash on
a heatsink made out of some special material. Is there any performance gain if your heatsink is made out of
copper? Does this really affect performance that much? I’ll try to shed some light on things,
and give you the lowdown on how to tell a good heatsink from a poor one.
Not a lot has changed since then on the theoretical side of things; heatsinks with lots of fine
fins or pins are still better than the ones with a few thick ones, and small heatsinks don't
suddenly outperform big heatsinks. What has changed, however, is the CPUs we are using
them on, with the Pentium III going mainstream, no longer just being the CPU of choice for
the big-budget computer user. With the Pentium II and Slot 1 Celerons slowly being phased
out, the heatsink manufacturers have released models adapted to this new mainstream
CPU. As the Intel Pentium III is the most popular CPU on the market, most heatsink
manufacturers have at least one model that will fit this CPU.
Furthermore all Intel CPU’s in the ‘Boxed’ version come with attached heatsink. So what is
actually the difference between a Pentium III heatsink, also known as a SECC2 heatsink,
and a Pentium II, SECC1 heatsink? If you look at the Pentium III cartridge you can see
that it is a lot more open than the Pentium II cartridge. With an OEM CPU, or with
heatsink detached , you can actually look right at the CPU and the cache chips. The way the
Pentium II SECC1 cartridge was constructed actually wasn’t that good a thermal solution.
The CPU and cache chips were enclosed within the cartridge and the CPU was thermally
interfaced with an aluminum backplate onto which the heatsink was attached. This might
seem reasonable, but if you are trying to keep the CPU temperature as low as possible you
must keep the thermal resistance as low as possible.
Thermal resistance is the (in)ability of the heat generated to dissipate, as measured in K/W
(Kelvin per Watt), an indication of the heat pumping ability of the heatsink. Obviously you
want this value to be as low as possible, so you want the minimum of material between the
CPU and the actual cooling device; in an ideal situation the CPU and the cooling device will
be directly thermally interfaced. Basically that’s the way the Pentium III , SECC2 cartridge
is constructed, the CPU core is interfaced directly with the heatsink, even without the
copper heatspreader, or slug, as found on the Pentium II.
With the 386 processor, there wasn't a need for a special cooling system. The chip was slow
and did not have many transistors, therefore the air flow from the power supply was enough
to cool the chip. With the release of the 486, cooling became an issue. With the slower 486s,
it wasn't a really big deal, but with the 486DX-66, cooling was an issue. This clock doubled
chip got pretty hot. From then on, chips ran faster and hotter. All chips used today require a
special cooling system. The type of processor is the biggest variable in the amount and type of cooling
needed. Run-of-the-mill fans could not keep it cool enough, so Cyrix had to design a special
heat sink and fan to keep their chip cool.
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