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Multi-Core Voltage Regulators To Increase Processor Efficiency
cylonlover writes "For decades, chipmakers strove to develop the fastest and most powerful chips possible and damn the amount of electricity needed to power them, but these days raw grunt isn't the only consideration. As more and more devices go mobile and these devices become more and more powerful, chipmakers must also take the energy efficiency into account. Harvard graduate student Wonyoung Kim has developed and demonstrated an on-chip, multi-core voltage regulator (MCVR) that he says could allow the creation of 'smarter' smartphones, slimmer laptops and more energy efficient data centers by more closely matching the power supply to the demand of the chip."
That's lame, even within their already lame marketing speech.
The three laws of thermodynamics:(1) You can't win. (2) You can't break even. (3) You can't even quit.
Including the same charts and graphs.
http://www.anandtech.com/show/1770
How this guy is going to get a patent on this stuff based upon his work in 2008 when Intel showed it onstage at IDF in 2005 is beyond me.
http://lkml.org/lkml/2005/8/20/95
So this is a way for an ALU (say) to send a message to to the MCVR saying "we need ten trillion electrons" when it is asked to a floating point multiplication, then the electrons get parcelled out and the ALU shuts down when the job is done. Sounds reasonable but there is still going to be a voltage regulator off the chip. This is more like an intelligent distribution system.
http://michaelsmith.id.au
Sounds similar to SmartReflex (tm) which is shipping on millions of phones.
http://focus.ti.com/general/docs/wtbu/wtbugencontent.tsp?templateId=6123&navigationId=12032&contentId=4609&DCMP=WTBU&HQS=ProductBulletin+PR+smartreflex
Where it differs is that there is an on-chip regulator to do the dynamic scaling.
The TI solution has a couple of regulators on-chip, with a couple of output voltages, as well as a more variable external solution.
The above device has variable regulators on-chip. (for annoying technical reasons, these are linear regulators, not switching,
so if they regulate to 50% output - half the (reduced amount of power needed) is wasted as heat.
CPU manufacturers have been caring about power efficiency for a vasy long time.
In fact, the first version of the ARM processor (in the 80's) was designed around its power usage so that they could use a cheap plastic carrier, rather than a very expensive ceramic one like all the competeing chips.
SJW n. One who posts facts.
I confess I am totally underwhelmed. Every chip I have designed since the 1990s (mostly wireless chips with embedded MCUs and DSPs, for portable applications) has had multiple voltage domains with multiple, independently controlled, on-board linear regulators -- sometimes as many as six or eight of them. Each MCU (and/or DSP) core always has its own regulator; it's the only way to meet the power budget of a mobile/portable product. Sometimes the voltage is dynamically controlled in response to processing requirements, and sometimes (if the processing requirements are relatively constant) the regulated voltage is designed to vary with temperature, so that at all times only the minimum voltage needed is supplied. (And yes, sometimes switching regulators are used, if the electrical noise can be tolerated in the application.)
ISSCC isn't known for accepting junk papers, so I'm hoping that what was actually presented (I didn't attend this year) was a novel on-chip voltage-regulation technique, and that the journalist has done a disservice to Kim by emphasizing the application, rather than the real novelty of his work.
The real problem with these designs is the interfaces between cores operating at different voltages. It's a PITA to do all the level-shifting to ensure that a core operating at 0.5 V can communicate with one operating at 1.2 V, ensure that one shut down doesn't affect one still operating, etc. There are lots of corner cases to consider (including transient effects while voltages and computing loads are dynamically changing), and a new technique to handle that reliably would be an advance in the art.
Lotsa fuzzyness in this blurb. Let's see if we can help clarify:
(1) First, these are not "voltage regulators". in the usual sense of something that takes an unregulated voltage and provides a stable, regulated voltage. They're the opposite-- taking a relatively stable main battery bus and dropping it down to various lower and possibly varying voltages. The goal being to sacrifice some speed and noise margin in order to use less power.
(2) Next: putting voltage droppers on-chip inevitably leads to much lower efficiency-- the only way to efficiently drop voltage is to use a switching-mode regulator, which not only generates a lot of electrical noise, it requires a big hefty inductor and capacitor, neither of which can be made on-chip. This on-chip voltage-dropping scheme cannot be any more efficient that using a plain old resistor, where you end up wasting a lot of power to get to a lower voltage.
(3) Dropping the voltage is not the only way to save power. In a pure CMOS chip you can scale down the clock speed and the power usage goes down by the same factor. This is a whole lot simpler, reliable, and more power efficient than dropping the voltage.
Based on what gizmag presents I'm not terribly impressed. There are several reasons to put the VR offboard. First is space, second is heat. A VR consumes a lot of both (relative to a microprocessor). You can easily see >5" square of space and >10W of power dissipation next to the processor (and everyone cries about it because of its location).
Since I don't see any resonant components included in the design it appears to me that this is a linear regulator, which will put out a lot of heat. In addition as it stands both Intel and AMD have the ability to dynamically scale the voltage they are being powered from. They can request a higher or lower voltage as well as (of course) draw more or less current, instantly, through their VID pins. So this sure doesn't sound like a great discovery, especially when you consider that the basic concept, as presented in the summary, is widely used and quite well known. But summaries by their definition don't tell the whole story, so perhaps there's more to it. I'll pull up the paper if it's available when I get to work.
As chip-on-chip technology becomes more widespread I will be interested to see what happens. It seems like there may be a place for "on chip" (as far as the enduser is concerned) voltage regulation with some of these all-in-one converter MCMs.
Just my $0.55 (US inflation, 1774-2008, for $0.02)
This motivated me to look up some of Wonyoung Kim's papers. This one is a good overview of his research. Very nice work -- but almost unrecognizable from the Gizmag article.