Inexpensive Home Building

Cut through the jargon and nonsense of home building and house construction by starting from zero dollars and trying to figure best-value bang-for-your-buck when choosing construction methods or construction materials. My research might answer some of your questions and at other times perhaps you have the knowledge or experience to post the answers to my questions and thereby help others too. The goal is an affordable and sustainable home for all.

Friday, December 29, 2006

Low-Watt Computers Offgrid Energy Efficiency

Save Money with Efficient Low-Power Computers

The airplane passenger’s computing problem is a microcosm of an off-grid system so we can use the jetsetter’s high-tech demands for our frugal needs. The choice is an old one: Increase computing by (1) increasing power (of the battery), or (2) decreasing usage (by the computer). We all know that conservation (minimizing load) is best. Minimize demand before you increase supply.

First, determine your needs. Many people overbuy. Not too long ago, I rigged a 100MHz machine to surf on DSL and it first-time-loaded most pages in a few seconds, used all email, used 128 encryption, and used some streaming video (but not most streaming video).

Next, realize that power consumption can vary even within a “name” processor. With the Intel Pentium 4, the ones with Northwood cores ran cooler than the ones with Prescott cores. New CRT monitors probably use less power than old CRTs but LCD monitors can use half the power of CRTs. Processors and monitors are two of the biggest energy hogs. Generally, speed needs power, so save money and buy a 7200rpm hard drive if you don’t need the speed difference of higher rpm (which most users probably wouldn’t notice anyway). For the power supply unit (PSU), many companies advertise peak power rather than constant load, PSUs operate best at 50-70% of capacity, "clean power" moderates power spikes and power surges, and PSUs have several sub-systems that each have a breaking point so you can crash if you exceed one limit even if overall draw is below overall capacity (plump for a high-quality PSU if you want peace of mind).

Laptops are more expensive because of (1) compact portability through custom "Form Factor" (FF) motherboards or smaller components such as the 2.5in. hard drive (on both “desktop replacement” and “mobile” models) and/or (2) power-saving technology (on mobile models). For instance, a “desktop replacement” laptop might have a cheaper “desktop” processor, whereas the mobile model will have a mobile processor that uses smart management (“power stepping,” etc.) to minimize power usage at ¼ of a desktop chip’s rated wattage (the proportion varies a lot by chip architecture).

Every chip maker has mobile versions of their chips. I think that Intel used “M” to denote its Pentium mobiles and now has a “Merom” chip. At least at one time, a laptop without wi-fi or other mobile accessories was a good indicator that it also lacked a mobile chip—but I’m not sure if that’s still true in the days of wireless home networks.

You have 3 basic choices:

  1. Get almost any good mobile-laptop deal on eBay. An older mobile might use more power than cutting-edge technology but it will offer good power economy at a steep price discount.
  2. Get a cutting-edge chip if the claims are true that it will draw 5W maximum (less than a compact fluorescent bulb, although that’s the chip and not the whole computer). Consider waiting longer until these become last year’s model.
  3. Get a custom computer that uses a mobile chip with a compatible power-managing motherboard in a regular desktop with common, cheaper hard drive and other components (although desktop drives use more power than laptop drives). This method can be more or less expensive depending on if you or a friend can buy and assemble the components from or elsewhere.

Compare computer components energy use.

Calculate computer components energy use to design your own computer system (watts calculator).


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