Menu Energy Efficient Computing
Energy saving PCUpdate: October 2008.
The parts for this PC were bought in 2004/2005. Processor and motherboard are not available any more in the shops.
There are more new, energy efficient processors and mother boards available now, but still they are not often used to save energy. You still will have to make an nerdy effort yourself, like switching off not used cores in a multi-core processor. Dynamic throttling (changing processor speed) and dynamic Vcore (variable voltage) of the processor still are not wide spread, you still need to tame your PC yourself.
The good news: My prototype inspired a new startup company to produce the TurtleStep PC.
Want to to see the results without all the nerd-talk? Scroll to the bottom!
Planning to buy a new PC, because I needed more power for editing images and audio, I soon found out a new PC would easily use twice the power of my current PC. This would also be the case while doing my daily work, which does not demand much speed. The cause for this is that the ICT-industry simply is not serious about energy saving (yet). So I set out to build my own energy saving PC. Not only to save energy and money, but also to show even an amateur like me can do this.
Aim: at least 2 speeds:
- A low speed for energy efficient and silent daily work, using about the same energy as my current 8 year old PC
- A high speed for editing 8 megapixel images and high resolution audio
- The ideal would be a 'throtteling PC', which adapts itself: Being almost asleep when I just read, E-mail and browse the web and only 'firing up' when I need the power to edit large images. Alas this was not (yet) possible with this setup, read on.
AMD Mobile Athlon XP-M 2600+
- 'Mobiles' are the best chips of a wafer
- Performs up to spec at lower Vcore -> more energy efficient
- Unlocked multiplier: variable processor speed
- Can be overclocked, but still needs less voltage than desktop processor
- 'Extreme' underclock/undervolt processor
Athlon XP 2600+ Barton
1917 MHz @ 166 MHz FSB, 11.5x multiplier, 1.65 Vcore, 68.3 watt
Mobile Athlon XP-M 2600+ Barton
2000 MHz @ 133 MHz FSB, 15x multiplier, 1.45 Vcore, 45 watt
Energy use at 2000 MHz, PC as a whole:idle stress Normal Athlon XP 1.65 Vcore: 99 watt 123 watt Mobile Athlon XP 1.45 Vcore: 84 watt 102 watt Saving: 15 watt 21 wattIn upper ranges inefficiency rises: 1.75 -> 1.775 Vcore (0.025 change) = 5 watt more
(Many processors don't run at optimum efficiency speed, but highest stable speed ...)
Abit NF7-S v2
- Overclockers darling with wide range of settings for voltages and speeds; lot of knowledge out there
- Selected because of low Vcore settings (down to 1.1 volt) and low multiplier (down to 5x); also good underclocker/undervolter
- Took out Nordbridge fan and replaced with passive cooler; added passive cooler to Southbridge (no essential modifications)
- Memory: Dual Channel mode, 2x512MB PC3200 Kingston Value Ram KVR400X64C3A/512
This memory does not do it's spec 200 MHz in dual channel mode which the motherboard offers, but dual channel still is a beter option than single channel. Better memory would allow for higher speeds, without raising energy use.
- Video: Asus 9550 (2005), passive cooled; low energy use
- Case: Aopen H600A, feature: air pipe over the processor fan to suck in cold air: fan speed can be lowered a bit more
- PSU: CoolerMaster 450W Real Power RS-450-ACLY, EU type, one of the most energy efficient in it's class and not too expensive
- Hard disks: Samsung SP4002H (40 Gb) and SP8004H (80 Gb); cool, so energy efficient
Issues down the roadThings I had to find out the hard way ...
- Motherboard not able to change processor multipier on the fly, need to reboot for switching to high speed.
Issue of all The Nvidia Nforce2 chipset motherboards?
The AMD PSTCheck program will do the trick, but is not availble to end users ...
- Both processor and Windows support the AMD 'PowerNow!' functons to do 'dynamic throttling': automatic adjustment of processor voltages and speeds, according to the actual need (like a laptop can).
It will never work on this motherboard and probably any desktop motherboard, the pins for accessing these processor functions are not even connected.
- A less effective, brute force way of 'throttling' works: a little program called CpuIdle simply stops the processor when idle and lowers both energy use and temperature. (So seems to do a much better job than the Windows 'idle thread').
CPU 1 = Comparable to my old 1997 Pentium 2 PC at 266 MHz, which uses 48-77 watt
CPU 2 = Energy eff. PC at 5x100 = 500 MHz speed: 50-53, with CpuIdle: 48-50 watt
CPU 3 = Energy eff. PC at 11x191 = 2101 MHz speed: 106-138, with CpuIdle: 93-116 watt
CPU 4 = Intel Pentium 4 processor at 3000 MHz in a game PC: 170-237 watt
(The 'A-brand shop equivalent' of my energy efficient PC).
So the energy use of my new PC at 500 MHz is generally always well below that of my old 266 MHz PC. And again demonstrates speed is not only about megahertzes: The responsiveness of the new PC is off the scale, even at 'only' 500 MHz, compared to the old 266 MHz PC. Much faster and much more memory, much faster hard disk access and transfers, much faster data-transport by the motherboard and the fast videocard all have a major role in making the new PC perform so much better.
I can do much more with less energy, that's progress ;-)
Compared to the PC from the shop at the same speed, it saves 45-51% electricity. In the 'light daily work' mode it saves over 70%. With real laptop technology the savings could be even better.
Note that both my old and my energy saving PC's have 2 hard disks. With only one harddisk (like the A-brand PC compared here) energy use would even be 6-8 watts lower.
Update October 2008: In the near future I will replace the two hard disks with one bigger hard disk and make my daily backup on a USB hard disk, which is switched off the rest of the day.