[conspire] Preparing dual-boot system

Ross Bernheim rossbernheim at speakeasy.net
Tue Jan 22 07:01:07 PST 2008

On Jan 22,  02008, at 3:09 AM, Rick Moen wrote:

>> Also, I'm not up on power supplies. I'm leaning towards making my  
>> next
>> machine a Micro-ATX one, and one of the reasons I didn't pick up  
>> one of
>> the 300 Watt Antec ones on sale for $30.00 at Fry's this weekend  
>> was be-
>> cause I thought that 300 Watts struck me as being too thin for  
>> safety's
>> (reliability's) sake.
> Yes and no.  Remember, we're talking in "hirohama"'s case about an
> eMachines box, all of which in my experience are physically small,  
> hence
> deliberately not expandable to (e.g.) hold multiple hard drives, have
> few slots, and usually have a single relatively low-power-draw CPU.   
> The
> real question is whether the alleged 270W Taiwanese no-name-you-know- 
> of
> PSU _really_ delivers the promised wattage -- whether it is a solid  
> and
> reliable 270 watts.  Cheap PSUs often simply cannot be trusted to be
> (even) as powerful as the label claims, and I'm inclined by past
> experience to believe, in that area, _only_ the labels of Antec,  
> Cooler
> Master, Enermax, PC Power & Cooling, and Sparkle/SPI PSUs.
> (There may very well be _other_ brands that are reliable.  I list  
> above
> the ones that have Worked for Me.<tm>)
> With one of the innumerable others, it might claim to be a kilowatt
> power supply, and _still_ overstress trying to deliver 200W to
> "hirohama"'s eMachines system and fry something.

There are a number of ways to cut corners in switching power supplies.
Since the stability and reliability of your whole system rely on  
correct power, the power supply is an important foundation of your  

Over rating the supply by either outright untruths or tests that favor  
strengths and ignore weaknesses of the power supply are quite common
among the lesser known brands. Use cheap capacitors that will fail much
sooner under stress. Use smaller capacitors so there is no margin of  
Use smaller inductors and the supply won't work as well in a brown out  
or with
surges or spikes.

Cut the capacity of one or more of the many voltages a modern power  
provides. Reduce the number of regulators and tie some of the voltages  
to the
main voltage. This is a subtle error as some of these voltages may sag  
under temporary load while all else is fine.

How big a supply you need depends on a lot of factors. On the other  
hand, other
than the gamers, a good portion of the industry is finally getting on  
board for the
idea of reducing power consumption. Recent disk drives are larger in  
capacity and
draw much less power than drives from only a few years ago. Newer CPUs  
made with smaller geometries and use less power for a given  
performance level.
If you go with an older less power hungry graphics card, it is  
possible to keep the
overall power consumption well under 300 Watts.

The biggest power guzzlers these days appear to be the top end Gamer  
cards with multiple shaders/renderers and GPUs and the Gamers are now  
multiple cards together! These are the guys who need 1KW or bigger  
power supplies.
I won't say these people are crazy, just obsessed. But their needs  
tend to warp the
industry. Having the task of buying some computers for work, I found  
it very difficult
to find a PC that didn't have gaming graphic cards. Your only choice  
among the major
suppliers is do you want a low end or high end gamer graphics card.

It is interesting to use a Wattmeter such as the "Kill A Watt" meter  
that you can get at
Radio Shack among other places. It is about $30. Put your computer on  
it and see
how much power it sucks from the wall. Multiply by .6 to .8 depending  
on the power
supply efficiency to get a quick approximation of the system wattage  


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