[LINK] How many Newspapers does it take to build Ayers Rock?

David Lochrin dlochrin at d2.net.au
Wed May 13 21:05:11 EST 2009


On Wednesday 13 May 2009 13:44, Glen Turner wrote:

> Electricity-wise you're saving what [with an X-terminal] over a 
> typical  corporate client PC?  Certainly the loss of a hard disk. 
> Maybe the move from a Pentium to a Atom class of CPU.  But 
> exactly those savings would be made by using a Atom-class 
> desktop with flash disk.

I was writing specifically about electrical power requirements.  But there's no reason why an X-terminal can't use a fanless low-end Intel processor with no hard drive and embedded Linux if that's a better cost option.

I don't have time to comprehensively research the energy savings, but here's one comparison I just happen to know about.  My HP d530 "small form factor" desktop requires 185 watts according to the Technical Reference, whereas the NCD 900-series thin client requires only 26 watts (both figures do not include the monitor).  These days a diskless Linux-based thin client would probably be a better way to go.

And you'd have to factor in the energy saved with lower (much lower!) support requirements.

> DC [power] is bad news. Getting rid of all those conversion costs 
> sounds really attractive, until you actually do it and realise that the 
> higher transmission losses of DC have eaten all of the savings. 
> And worse, that higher loss --> higher current --> thicker cabling 
> and the whole exercise turns insanely expensive and using 
> CO2-expensive materials.

OK, I think you've convinced me.

> So we're headed back to AC as the preferred power source for 
> networking equipment, [...]
> 
> What will be different this time around is that the efficiency of the 
> power supply will be required to be high, and that cheats like low 
> power factors will be removed by benchmark specifications.

A low power factor won't affect the efficiency of the equipment much.  The power factor of a compact fluorescent lamp (CFL) is around 0.6 and they're still being used to phase out incandescent lamps; in fact AS/NZS 4847.2-2008 only requires a minimum power factor of 0.55.

David


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