Cooling your PC
Modern PC's are running hotter and hotter. Each new chip has a higher thermal dissipation than the last, and this goes for graphics cards and memory as much as for the CPU. The days of passive heatsinks are over now for most of the pc, motherboards have often got active (ie a fan) cooling for the chipset and very few graphics cards have passive cooling now.
This article will attempt to give the user a solid grounding in the basics of pc cooling at the moment. There are a huge number of factors that influence the type of cooling that you will need in your pc - the hardware itself, the choice of case and the environment that the system will be used in. The environment is 2 factors, the ambient temperature in your room will dictate the capacity of the cooling system that you need and the noise level that the you can tolerate will dictate both the type and the cost of the cooling system. A really quiet, relly fast system is very costly to build, as there is a lot of thermal energy to remove, and the traditional ways of fast hi flow fans just won cut it on noise levels.
A Brief History Of cool
The early computers needed no special cooling. Take the top off any old computer (Amstrad, Commodore, Atari ST etc) and you can see the top of the microchips bare. They generally had vented cases but no real heat problems, and no fan in the power supply.
PC's came along, and they usually had 1 80mm fan in the power supply which blew air into the case accross the power supply components. 286 and 386 processors had no heatsink most of the time and ran hot to the touch but well within the limits. 486 processors started to sport aluminium heatsinks bonded to the top of the chip to improve cooling as hey could crash in high ambient temperatures. At some point, the power supply fan was swapped to be an exhaust fan - blowing the heated air from the power supply in to the case was never a good idea. Now the lower pressure inside the case caused cold air to be dragged in across the CPU etc and then the air went through the power supply and all was well.
When the Pentium came along, It became necessary to add a small cooling fan on top of the CPU heatsink. The power dissipation of the Pentium CPUs was between 10.1 and 15.5 W.This was often a 40mm fan, and added some noise while forcing air accross the CPU. The Pentium could burn out if the heatsink fell off, and was the first on the new socket 7 platform, which had a ZIF socket for the CPU and then the heatsink / fan (HSF) clipped over the top using a sprung clamp engaging on two lugs. The later motherboards had special power feeds for the fans which monitored the RPM of the fan and could sound a warning if the fan died. Passive cooling was still possible, but needed a large heatsink and careful design of the case to ensure enough air was dragged acros the heatsink.
The Pentium II was a totally new design - it fitted into a slot and was encased in an alloy cartidge. A heatsink was then clipped on to the cartridge over the chip itself and the cache ram. The fastest CPU of the time was becoming something of a room heater: the 250 nm design resulted in a maximum thermal dissipation for the Klamath of 43 W. This is up to 4 times as much energy as the pentium! Again, the PII could be passivly cooled, but the design had to be just right. Companies like Dell and Compaq made computers were the fan in the psu dragged air through the system and cooled the CPU, but these systems were like a wind tunnel and had propriety motherboards and heatsinks as well as often mounting the processor paralel to the board to aid air flow. The heatsinks got larger, but the fans were still little 40mm units due to space considerations - just made to spin faster and shift more air. A front 80mm case fan as a forced inlet bacame popular with these systems, particularly when multiple drives were fitted.
Around 1997, 3d accelerator cards started to appear on the market. This put another processor inside the PC and produces yet more heat. The voodoo was