Re: VCool - cool your Athlon/Duron during idle

["Paul G. Allen" <pgallen@randomlogic.com>]

Liakakis Kostas wrote:
> 
> On Mon, 27 Aug 2001, Kurt Roeckx wrote:
> 
> > On Mon, Aug 27, 2001 at 02:48:24PM +0300, Liakakis Kostas wrote:
> > > On Mon, 27 Aug 2001, Jan Niehusmann wrote:
> > >
> > > > (asus writes that one of the problems that can happen with this power
> > > > saving mode are the huge changes in power dissipation, from 60W to 5W
> > > > and back - therefore I assume the power saving mode can save up to 55W)
> > >
> > > The problem they are describing is not the change in power dissipation,
> > > but the change in current draw from the regulated 1.75V (difference of
> > > about 30A or more).
> >
> > And what do you think power is?
> > Maybe it's the voltage times the current?
> 
> Your point being? This is power yeah. However I can get 50W with 1V@50A
> and with 50V@1A ... tell me which will be easier for a regulator when
> going from 10 to 50W while trying to keep the voltage steady.

First of all, let me say that I used to run the lab at NCR Corporation testing and qualifying power supplies, and making design recommendations/changes when
they failed, for main frame computers. 

That would depend upon the power supply, and specifically, the regulator design. Consider that the average PC user buys a cheap $30 - $50 (US Dollars) case and
P/S package. That P/S will never be able to handle this kind of transition and stay within its specified regulation. In the electronics industry, you get what
you pay for (with the exception of a couple of big names that simply sell junk 'cause they can), and there's no exception to this rule when it comes to power
supplies. I have tested PC power supplies by various mfgs. and have found that most do not hold up to the specifications printed on them, let alone to anything
a CPU/MB mfg. may require. Many operate on the fringe of their specified voltage range even under low load, send them up to maximum load and they quickly fly
south (and many never return!). In simple terms, you won't find a P/S under $100 (US) that will be worth the CPUs weight in regulation, let alone will be able
to handle such a large power transition.

> 
> So to rephrase myself the condition of less power dissipation (and that is
> thermal output, not power consumption which isvoltage times current... )
> is the result of less current draw of ~30A. This is a huge difference. And
> this is the problem. There are regulators on certain motherboards which
> can't cope with this. And they increase (not that bad unless you fry a
> chip) when current drops, or decrease voltage when there is current need
> (crash) of the tolerance limmits.

MoBo regulators aside, as stated above, most power supplies can't handle it, so there's nothing the regulator could do no matter how well designed it is. What I
said above does stand for on-board regulators as well. 

BTW, there are two basic power ratings for an electronic component - Power Dissipation (Pd) and Power Consumption (Pc). Pd is the amount of power (V*I or
Voltage times Current) that the component wastes in heat (which is generated by the friction of electrons moving through the component). Pc is the total power
required by the component for operation, and is a function of Pd plus the power actually used by the component and not wasted in heat. Pc is also V*I. Pc is
measured by connecting meters (voltage and current) to the power connections on the component while in operation. Pd can be measured by the amount of heat
coming off of it, or by various other methods. Both Pd and Pc can be decreased by turning off portions of the component, decreasing clock speed (thereby
decreasing friction), and by decreasing voltage and/or current to minimum operational levels. It can be increased by turning off the wrong portions of the
component causing others to exceed their specifications, by increasing clock speed, by increasing voltage and/or current to maximum operational levels (or
beyond - a Bad Thing :), and by decreasing voltage and/or current below operational levels. The last scenario causes the component to do all kinds of things it
wasn't meant to do, which usually causes Pd to rise dramatically and therefore Pc follows.

So, in summary, I wouldn't use power saving modes (and I don't) unless:

1. I had 100% conviction that my P/S would meet or exceed the required specifications.
2. I had 100% conviction that the MoBo would meet or exceed the required specifications.
3. I had 100% conviction that all components in the system would meet or exceed the required specifications.

More often that not, they don't, and most consumers are none the wiser. I have never used any power saving mode because in any given case the system in question
could not meet 1 - 3.

PGA

-- 
Paul G. Allen
UNIX Admin II/Programmer
Akamai Technologies, Inc.
www.akamai.com
Work: (858)909-3630
Cell: (858)395-5043