Why can't we scale the frequency of a processor to a very low value?

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Blandge

Member
Jul 10, 2012
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Actually there is a minimum operating Voltage. That is what you need to actually be able to open a transistor gate, and was around 0.6V or so, if memory servers me correctly. I recall an article in Wikipedia mentioning that, it was called Threshold Voltage. I also recall experimenting with that during 2010 with a massive undervolt and underclock of a Deneb RB-C2, and wasn't able to get under 0.6V.
http://imageshack.us/a/img694/6695/undervolt.jpg
http://imageshack.us/a/img693/7742/undervolt2.jpg (Imageshack resize seems to have killed it)
http://imageshack.us/a/img696/5256/undervolt3.jpg


Current Power Saving techniques are based on shutting down parts that you don't need instead of making them work at minimal Frequencies. I still think that a massively underclocked and undervolted Processor may be useful if you want to keep your computer on because you like to leave all your Instant Message applications, uTorrent, etc, open and ready to use. Power consumption from the Processor itself will be minimal in such state. But its the rest of the system power consumption what kill the power efficiency of doing so, not the Processor itself.

There is actually a technology called subthreshold computing where one uses the subthreshold current (leakage) to do useful work.

There is another field of study referred to as near threshold computing which is also quite cool.
 

IntelUser2000

Elite Member
Oct 14, 2003
8,686
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S0ix isn't actually supported by most Haswell chips in laptops. It's only supported in Y and U series SKUs, so basically ultrabooks and tablets. I'm rather skeptical that ultrabooks would actually make use of it, though. Connected standby is essentially useless for anything other than tablets and phones.

They do, its one of the reasons for greatly improved battery life.

The lowest power version of S0iX is needed for Connected Standby, but general power saving principle applies even without it.

Also, the wake time of the 4th Gen Core Ultrabooks and Tablets are pretty short. I assume they use it in some form.
 

IntelUser2000

Elite Member
Oct 14, 2003
8,686
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Hi,

Everyone here talks about overclocking. Obviously the thing stopping us from overclocking is the temperature.But I just feel curious why we also can't undercloking too far:rolleyes:

I am not sure what you are asking, but if its about power use, I can answer that.

There's no point in running at below 800MHz. That's what C-states and S-states are for. You can just turn off the whole thing with minimal latency, which is even lower power.

The reason its at 800MHz is because some applications are specifically coded to run at 800MHz. Why? To save power. It's very light load so you don't need top frequency, but you need certain level of performance.