Can CPUs Make PCs Faster & Quieter?


Engineers have long believed that fast, cheap and good capabilities are easy to achieve as long as you try to achieve only two of them simultaneously. It is even more difficult if you try to achieve all three at once. Until recently, the same has been true with a slightly different triumvirate: namely, fast, good and quiet. Based on the two different systems we put together for this story, we can't claim to have eliminated noise completely, given our requirements for speed and capability, but we can claim to have brought noise down to a level acceptable for entertainment and office use.

Causes And Characteristics Of PC Noise

In the simplest of terms, moving parts cause noise in PCs. Any fan or device with a built-in fan (power supply, graphics card or PC case), or any device with moving parts - including optical and hard disks, floppy drives and so forth - make noise. In general, bigger, slower moving fans are preferable to smaller, faster moving ones for several reasons. This is mainly because fast and small fans create higher-frequency noise that is more likely to be audible and possibly even objectionable, and that keeping components cool requires smaller fans to turn faster and work harder to move the same amount of air as larger ones. By spending more money on fans and fan controllers, it's possible to reduce noise output from PCs dramatically, especially if you include the purchase of more efficient power supplies with larger fans as part of this overall process.

When it comes to drives, the best thing to do is to seek out reviews that provide information about their sonic characteristics as well as their speeds and feeds. When we work with magnetic or optical storage devices, we always try to keep our ears wide open to get a sense of how they sound, as well as performing a whole battery of measurements to determine how they work.

When it comes to quieting down PCs, especially for media center use, we've learned to factor in various types of choices when picking components for such situations. Here's a brief summary of some important criteria that we put to work in general when building media PCs, and to which we pay increasingly close attention as quiet operation moves up the priority scale:

  • Avoid small fans: By small, we mean anything under 80mm in size, with 90mm, 120mm, or even larger fans preferred for case ventilation where needed. Larger fans are particularly amenable to use in tandem with speed controls, and make much less noise when turning slowly than at higher speeds. Among the implications of this design decision means that a system will not have motherboards with chipset or other small fans or actively-cooled graphics cards. The only fans smaller than 120mm in either build for our tests were on the CPU coolers: a 92 mm model for the QX 6800, and the petite socket 479 cooler that Asus includes with its N4L-VM motherboard (coolers for mobile CPUs are not widely available as standard parts, so we were grateful that this 70 mm fan was quiet).
  • Exercise great care in choosing a power supply. Power supplies invariably include fans nowadays, but those with larger fans tend to be quieter than those with smaller ones, and more efficient power supplies tend to require less active cooling than less efficient ones. For this story, we concentrated entirely on PSUs in the 80-plus percent efficiency bracket, and ultimately went for a medium-power (450 W) PSU that was both very efficient and very quiet, offering 85% efficiency at 225W (half-power) and incorporating a quiet, dual ball bearing 120mm fan with active thermal control.
  • Choose all drives for low noise output as well as for technical capabilities. Most hard disks are reasonably quiet nowadays, though some are quieter than others. We picked the new Seagate 7200.10 PMR (perpendicular magnetic recording) 320 GB drives for this build because they're pretty fast and among the quietest 3.5" drives around. We chose a half-height Toshiba HD-DVD player to bring high-definition media to the system, that was reasonably quiet after initial drive spin-up (but noisy for up to one minute during spin-up, as so many optical drives can be).
  • The case for a quiet PC is an extremely important element, for several reasons. First, it provides the cage in which all components get mounted, and where mechanical contact can conduct sound. Second, it determines the length of the noise path from the user's ears to the sources of noise inside the PC (the longer the path, the quieter the PC will sound, as will become blindingly clear in the noise measurements section later in this story). Third, it provides the apertures and mount points for any case fans used for system ventilation (primarily case fans used to draw air through some outlets, and blow it out through other outlets). Fourth, case designs can make good use of sound insulation to direct sound out the longest sound path.
    We chose the Coolermaster Cosmos 1000 case for our builds, because it features silicon insulation on all drive mounts, offers a lengthy sound path from sources of noise to the user's ears, includes four quiet 120 mm fans (a bottom intake, plus two top and one rear exhaust fans, with an aperture and mounts for an optional fifth 120 mm fan for hard disk cooling). It also has a wind tunnel for graphics cooling, and features built-in acoustic foam insulation on both removable side panels. The Cosmos 1000 is a large mid-sized tower case with dimensions of 10.47" x 23.54" x 27.75" (266 x 598 x 628 mm, WHD). At that size, it's quite capacious, and includes 6 or 7 3.5" drive bays as well as 4 or 5 5.25" drive bays (you can convert one 5.25" drive bay into an exposed 3.5" drive bay, or use it as a 5.25" bay instead).
  • When building a quiet PC, it's also important to pay close attention to the power requirements for system components. That's because less power draw means less heat output, which lowers cooling requirements, and thus also reduces the noise the system must make to operate properly. Of course, lower power parts also tend to last longer and cost less to operate as well, so there are many side benefits from this criterion, though such parts do tend to be more expensive.

In trying to satisfy our desires for high performance as well as quiet operation, we decided to try out two stars in the Intel processor lineup. First, we chose the Intel QX 6800 (2.93 GHz) quad-core processor and the passively-cooled Gigabyte GA-P35T-DQ6 motherboard for one of the fastest of desktop processors currently available. Second, we chose the Intel T7600 mobile dual-core processor and the passively cooled ASUS N4L-VM DH motherboard for the near-top-of-the-line T7600 (2.33 GHz) Core 2 Duo mobile processor. We chose these CPU designs so we could compare a part deliberately designed for lower power consumption against a faster, more powerful desktop alternative.

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