Boston Linux & UNIX was originally founded in 1994 as part of The Boston Computer Society. We meet on the third Wednesday of each month at the Massachusetts Institute of Technology, in Building E51.

BLU Discuss list archive


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Discuss] Cool Processing



You're assuming changing the voltage changes nothing else, if you try to
apply Ohm's law directly.  Many other things change when you change the
supply voltage of a semiconductor/PCB.

Among them:
Switching thresholds
Edge rates
Leakage currents
Capacitance of most of your capacitors

*Drew Van ZandtArtisan's Asylum Board of DirectorsFirefly Arts Collective
Board of Directors*

On Fri, Jun 19, 2015 at 1:26 PM, Joe Polcari <joe at polcari.com> wrote:

> And ohm's law doesn't apply why?
>
> Sent from my iPhone
>
> > On Jun 19, 2015, at 1:23 PM, Richard Pieri <richard.pieri at gmail.com>
> wrote:
> >
> >> On 6/19/2015 11:02 AM, Steve Litt wrote:
> >> Today I have a 16GB RAM box, with dual core CPU (I wanted things to
> >> stay cool),
> >
> > I think I recently mentioned buying a new notebook. If I didn't, well I
> am mentioning it now: a Mythlogic-branded Clevo P750ZM. It has a Core
> i7-4790K processor. You read that right: a 15" notebook with a socketed
> Devil's Canyon i7 desktop CPU. I think I have some grounds for saying that
> limiting yourself to 2 cores is a poor way of managing heat.
> >
> > AMD and Intel processors draw substantially more power than they
> actually need. Every processor is different and the minimum stable power
> varies so they ship with the stock power draw set high enough that all
> processors in a series will run stably. Excess power turns into waste heat.
> This is why my i7 quickly reaches 99C under load and throttles if I don't
> do something about it.
> >
> > That something is called undervolting. As the name suggests it means
> reducing the voltage that the processor draws. Since every processor is a
> little different there is no single ideal undervolting setting. Finding the
> ideal for a given processor requires some trial and error, same as
> overclocking. A common starting point for Haswell i7 processors is -80mV
> dynamic CPU voltage offset and -100mV processor cache voltage offset. My
> 4790K barely reaches 80C with Intel XTU's stress test with these settings.
> That's the same as the i7-4790S at 3.2GHz (what the notebook originally
> shipped with) while running 20% faster at 4.0GHz. I figured that was good
> enough and called it done.
> >
> > --
> > Rich P.
> > _______________________________________________
> > Discuss mailing list
> > Discuss at blu.org
> > http://lists.blu.org/mailman/listinfo/discuss
> _______________________________________________
> Discuss mailing list
> Discuss at blu.org
> http://lists.blu.org/mailman/listinfo/discuss
>



BLU is a member of BostonUserGroups
BLU is a member of BostonUserGroups
We also thank MIT for the use of their facilities.

Valid HTML 4.01! Valid CSS!



Boston Linux & Unix / webmaster@blu.org