For many people the easiest way to get an efficient computer is to purchase a laptop/notebook. Most use between 20 and 30 Watts of power when operating and up to about 60 Watts while charging the battery. They feature a variety of power saving modes all designed to extend the life of a battery. They are portable so that they can be used anywhere. There are laptops available at reasonable price ranges that are comparable to desktops so as this difference in price narrows a notebook could be the better choice for many.
Despite the advantages of a notebook sometimes a conventional desktop is preferred. In my case a machine designed to operate 24×7 and with the ability to add pci expansion cards. I decided to put together a pc that uses an amount of power similar to a laptop but that is also quiet and uses commodity parts as much as possible. I want the possibility of a mid life upgrade and the freedom to choose a custom combination of parts. This machine is not intended to be a game machine but will certainly be suitable for old and light gaming. It may end up being a combined personal video recorder/terminal server for diskless clients (MythTV)/phone switch & voicemail server (Asterisk)/file server as well.
Throughout the quiet, low power consumption PC there is a need to use less power, waste less power through heat and use less power removing that heat. Therefore there are several key, guiding requirements for a machine like this:
- Very high efficiency power supply with a quiet or no fan.
- Low power consumption, up to 45W cpu’s from AMD.
- Integrated video on the motherboard.
- Use large fans rather than small ones since they usually move more air per rpm.
- Big, quiet low rpm fan for the case.
- Big fanless heatsink for the cpu.
- 2.5″ sata hard drive.
Power Supply
Just as it is important to match the power needs in a high performance gaming rig it is equally important to match the power needs in a low power consumption computer. Normal power supplies waste a great deal of energy and mostly through heat. What is worse is that the amount of wasted energy can be high at low energy consumption levels. There is an effort to convince manufacturers to get their power supplies certified 80Plus which means that their power supplies are at least 80% efficient or greater energy efficient at 20%, 50% and 100% of rated load. For my machine I have chosen the PicoPSU-90 from Mini-Box. It is rated at 96% efficiency, has no fan and is very small (great case modding potential). It is a DC-DC power supply so there is an external 80W brick power supply. When operating at low wattage this power supply has a great impact on the total amount of power used. Compared to my next most efficient power supply it uses about 10W less power.
Low Power Consumption Processor
Since the Pentium 4 there has been a bit of a renaissance in CPU design both AMD and Intel are producing variations of desktop processors that are much more energy efficient. Once again, less power usually means that less heat needs to be dissipated. For this machine I have chosen the AMD Athlon X2 BE-2300. This processor runs cool enough to use a passive heatsink and just the case fan for air flow. I would probably choose the AMD Athlon X2 4850e processor if I was purchasing new today since the processor sweetspot keeps changing.
Motherboard with Integrated Graphics
Discrete video cards can use a great deal of power. They are absolutely essential to play the latest and greatest 3d games at high frame rates. For most of the rest of us however, the right motherboard with integrated graphics will be more than enough.
The best choice is always a moving target. Right now the AMD 780G based boards are very popular but for this machine I have chosen the Biostar TF7050-M2. It features the GeForce 7050PV/NF630a chipset which is comparable to the AMD 690G based chipset. Although it will work well with Vista it is a good match for Windows XP. The AMD 780G and newer Nvidia chipsets are better optimised for Vista but may use more power. This board should be able to use video acceleration on both windows (PureVideo) and linux (XvMC). From what I understand newer Nvidia chipsets may have dropped XvMC support or Nvidia may have not committed to supporting it in newer versions. This type of video acceleration is important since it allows the graphics processor to do more of the work while allowing the main processor to do other things.
I prefer mATX motherboards due to the flexibility of being able to install in smaller cases than full ATX motherboards. The Biostar TF7050-M2 also suspends and resumes nicely with both windows and linux (I won’t need this if it becomes a media server). This motherboard also features GB Ethernet which may be useful if this machine ends up as a media server.
Fans and Cooling
My PC has just one 92mm fan. It is a Nexus Real Silent Case Fan that has been slowed down to 1298rpm by using a Zalman Fanmate fan controller. The cpu is being cooled passively with a Scythe Ninja Mini. At Idle the cpu operates at 25-29°C at an ambient room temperature of 20°C. A case that has has a 120mm fan replaced with the 120mm Nexus Real Silent Case Fan would be better but the one I used was priced well. A larger fan will move more air in each revolution of the fan. It is hard to take the word of vendors about the level of silence of their products. These products were selected based upon the “Reference” section of silentpcreview.com
Storage
This machine has the IDE LG GSA-4163B DVD-RW. I don’t use my DVD drive most of the time. I think an external eSATA drive would be a better alternative. It would have maximum performance, be able to be moved to another machine if needed and it could be turned off when not in use. It is convenient mounted internally, however, and does not seem to use a significant amount of power when idling.
The hard drive is a 120GB Seagate Momentus 5400.3 (ST9120822AS) 2.5″ SATA drive. It is normally intended for laptops but on a desktop it is also a quiet, cool, low power consumption option. It is not as fast as a normal 7200 rpm, 3.5″ desktop drive but it uses a fraction of the power at 0.8 to 2W compared to 10-12W for the normal desktop drive. There are plenty of options here. There are newer 2.5″ drives that operate at 7200rpm such as the Momentus 7200.3 that only use a little more power (0.75-2.3W). There are also newer 5400rpm drives such as the Momentus 5400.5. The Western Digital Scorpio hard drives are good as well. A major difference between 2.5″ and 3.5″ hard drives is that 2.5″ drives usually cost more per GB but that gap is narrowing for 160GB and 320GB sizes. For very large hard drives there are the Western Digital Caviar Green 3.5″ hard drives at 2.8W to 5.4W in 500GB, 750GB and 1TB sizes. They are not as fast as the other Caviar series drives but they are more than fast enough for bulk storage.
Result
Lets face it, there are faster machines out there. The purpose of this machine is to act as a silent, power efficient, general purpose PC with the possibility of some backend services running on it 24×7. It does the job well. With Windows XP it idles at 26W and suspends at 4W. While running benchmarks it uses 56W. With Ubuntu 8.04.1 running from livecd it idles at 27W and runs glxgears with the NV video driver at 54W. It is well under the 80W limit of the external power brick and gives me plenty of power budget room to add a tv tuner card and an extra hard drive if needed. The machine is quiet. I can tell it is on since I have the fan speed turned up to a comfortable level for me. Silence can be a subjective quality. I could turn it down closer to 1000 rpm if I wanted to.
The normal enthusiast seeks to maximize performance but this article is about optimizing power consumption for a machine that operates 24×7. This is a different way of thinking about PC’s than most are used to. I hope is becoming more popular as people consider the operating costs of the devices they use.
Part List
* Prices in Canadian dollars unless otherwise noted.
PicoPSU-90 DC-DC Power Supply & 80W AC-DC External Power Supply
& Bracket – $93.56USD + $41.12CDN UPS brokerage charge
(Paid way too much importing from US supplier, mini-box.com, consider ordering from ncix.com ($57.31, Sept. 25, 2008) and avoid UPS brokerage charges. Kit from NCIX includes a 60W external power supply so you may need to also source a larger 80-90W external power supply)
AMD Athlon X2 BE-2300 Processor – $69.55
(BE-2300 is obsolete, consider newer Athlon X2 4850e at directcanada.com)
Biostar TF7050-M2 Motherboard – $70.80
(directcanada.com, may be wise to consider newer Nvidia 8200 or AMD 780G based motherboards)
2 x 1GB Crucial Rendition, 667 Mhz, DDR2 Memory – $24.99ea – $49.98
(available from ncix.com)
Nexus 92mm Real Silent Case Fan – $14.54
(available from ncix.com)
Zalman Fanmate – $3.77
(available from directcanada.com)
Scythe Ninja Mini CPU Cooler – $39.99
(available from ncix.com)
Microcentre Powerspec mATX Case – $25.00
(was on sale, ymmv)
LG GSA-4163B DVD-RW Drive – ~$30.00
(many newer drives available in this price range)
Seagate Momentus 5400.3 2.5″ 120GB SATA Hard Drive – $55.95
(ST9120822AS)
Resources
silentpcreview.com – The authority on silent computing.
The Reference section and forums are especially helpful.
