Chipmakers Admit Your Power May Vary

Dylan Knight Rogers writes to mention a News.com story discussing the realities of chip power consumption. From the article: "Assessing only pure performance is passe. The debate these days is about performance-per-watt, which seems like it should be a simple miles-per-gallon type of calculation. However, miles are miles, and gallons are gallons. There's no one simple way to measure processor performance, and measuring the amount of power output by today's chips is proving just as difficult."

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How is this news?

[AuMatar]

Performance being difficult to measure is well known- you can't go by clock speed, or even clock speed*instructions per clcok since these will differ based on instruction mix. For power, a simple inverter will use different amounts of power depending on if its on or off- exact power for a chip is impossible to guess. This is all old news.

Re:How is this news?

[dsanfte]

Uh, actually, watts sucked per hour/minute/etc has been very easy to measure for many decades now. There is no reason why chip wattage drawn should be difficult to gauge in the slightest.

Re:How is this news?

[kfg]

Performance being difficult to measure is well known. . .

it should be a simple miles-per-gallon type of calculation. . .

It is. That's the problem. Mr. Krazit seems to be utterly clueless. I defy him to predict the milage I get the next time I go out for a drive.

Hasn't he ever noticed, like most of the rest of us have, that the milage he gets is not actually the same as the EPA test "prediction"?

That's because the EPA test only gives valid results for. . .the EPA test, which is actually an average of multiple tests.

There's no one simple way to measure. . . gas milage. Sheesh.

KFG

Re:How is this news?

[Firethorn]

they only tolerate a fraction of a milliohm of added resistance

Say what? They're not [i]that[/i] intolerant. Otherwise the overclockers wouldn't be playing around with increasing the voltage. Normal power supplies would have to be far better, and motherboard power compensators far more expensive. Besides, if your measurement device adds that much resistance, you simply increase the voltage of the rail a smidgen to compensate.

Now, I am talking about doing all this in a lab, for best results.

The true difficulty comes in that the measurements are highly dependent upon what you're doing with the CPU. Acting as a webserver, managing database access is a totally different from calculating weather patterns, for example. Different CPU's have different performance for their floating point systems, integer, memory operations, etc...

Not indicative of real world performance

[0racle]

So it's exactly like the miles-per-gallon on new cars.

benchmarks

[Anonymous Coward]

This is what benchmarks are for. Compare the performance of two systems with other variables held as constant as possible. This has been going on for years, has it not? If I want a computer to play games, I see what different CPU configurations yield in, say, HL2 with the same ram and video card.

Is this perfectly scientific? No.
Is it practical? Hell yes!

Re:benchmarks

[KermodeBear]

This is exactly how I feel. Theoretical speed is nice and all, but just where does theory and practice meet? Usually never. It's the practical application that matters, which is why, in my opinion, benchmarks of common operations are important. Things such as frames per second in a video game, or how long it takes to encode a DVD, or how long it takes to open up a large PDF... Those are things that matter and, perhaps more importantly, things that the average joe can wrap his mind around. How many Joe Users know (or care) about stuff like clock speed and cache size?

Some miles are up hill and some are down hill...

[EmbeddedJanitor]

Especially with caching and pipelining, MIPS per W gets very difficult to measure. If you can live in the cache you don't need to go fetch from the outside world. If you stall the pipeline, you lose performance. Some operations (eg. DIV) clock a lot of transistors, some (NOP) don't. It was a lot easier to measure MIPS/W when devices were synchronous. Now they're a group of asynchonous entities (core CPU, cache,...).

BTW, EPA mpg are measured without using real mile on real roads.

Well...

[radish]

Miles per gallon are hardly constant either. Uphill? Downhill? 10mph or 100? Highway or city? Same difference.

Re:Well...

[smoker2]

That's why manufacturers base their MPG figures on something called the Urban Cycle.

This takes in slow city traffic, faster freeway traffic and top speed travelling, approximate to an average consumers car usage.

It's not just the CPU

[Rosco P. Coltrane]

For most users (i.e. not power-users doing heavy calculations for some scientific purpose, or high-quality video editing, or raytracing), most processors provide way more power than needed, and have done so for years. Or at least, they *would* provide all that power if the software running on top of it wasn't bloated and unnecessarily complex, unoptimized and badly written. And no, I'm not just talking about Windows, I'm including Linux, MacOS and all the others in the bag.

The best proof that modern software makes modern hardware suck is that, back in the mid-eighties, I used an Atari ST to do desktop publishing, and it wasn't all that different from what I can do now with a simple PC that would look like a supercomputer back then.

Re:It's not just the CPU

[Burning1]

As a resource becomes more plentiful, uses for that resource also increase. A similar example from automotive engineering comes to mind:

Because of advances in engineering and design, engines are far more powerful and efficient now than they were in the early 90s. Cars have far better aerodynamics. However, gas mileage has not improved. In many cases it's gotten worse since the 80s. Likewise 0-60 times haven't improved much.

So what happened? Instead of improving the performance of your average family sedan, auto makers have added better armor, more air vents, more lights, DVD players, and more plush materials. Everything is safer and more comfortable now than it was in the 80s and 90s.

My 86 Camry will beat your 2007 Camry in a drag race and it will get better fuel mileage. But for a 500 mile trek across California or a bad accident? I know which one I'd prefer.

Likewise, my Pentium 4 has 16000 times more ram than my first computer (a C64,) and 256 times the ram of my first 486 (side note: how long before someone informs me of the amount of ram my 486 had?)

My 486 could write a document just as easily and with as much style as my P4. But it couldn't write a document while I was watching a subtitled MP4 movie in another window, listening to music, burning a DVD, and downloading hot lesbian pr0n from bit torrent. And it certainly couldn't do all that on dual 20 inch widescreen flat panel displays.

Sure, software is more bloated. But like the 2007 Camry (available wherever fine cars are sold,) after a long day your ass is going to be a lot more comfortable.

Re:It's not just the CPU

[kfg]

like the 2007 Camry (available wherever fine cars are sold,) after a long day your ass is going to be a lot more comfortable.

My ass has never been as comfortable as it was in my '67 Triumph GT6. Don't ask about my right leg resting against the tranny case though.

When I wear shorts I just tell people it came from shrapnel at Anzio.

KFG

Re:It's not just the CPU

[NutscrapeSucks]

My 86 Camry will beat your 2007 Camry in a drag race

I recently read an article noting that the 2007 Camry (with 250HP or whatever) will out drag race most sports cars from the 1980s, much less the sedans. Although, greater point taken about bloat.

Re:It's not just the CPU

[bigtreeman]

You young people have it so easy,
when I was young....
TTL was hot and fast
CMOS was cool and slow
a fave joke was about the Russians designing the worlds largest micro chip
these days its not a joke its reality
CMOS is hot enough to cook an egg
hard drives shut down from over heat
components accelerate their aging when running hot which they always are
in summer you have to be in air con or have multiple fans
I now always have a 4" fan on my cpu

V8's are becoming dinosaurs

the next generation is 128bit processors
then 256bit

put some intelligence back into hardware and software design
throw away the sledgehammer
slim down, speed up

cool dude

Re:It's not just the CPU

[cgenman]

The brother post may have used a car analogy, but he's basically right. There is a similar situation in Game Development.

Right now, you have machines that will do amazingly powerful things, especially with the Next-gen coming out. So what do you do with that power?

Quite simply, one of the things you can do is optimize less.

For example, early FPS games were written largely in assembly in an attempt to eke out every bit of power from the system. It worked, but it was really expensive financially and broke at the slightest provocation. But as computer power increased, you started to be able to write parts of your game in C, and use assembly for the rendering and other intense processes. Then you could write parts of your game in script, and your engine in C. Each step up the chain gets easier to maintain and extend, but at the expense of more clock cycles.

Another example of the above is simple data abstraction. On the NES a simple boss, like Frankenstein, would need his own code base and optimizations to get him to work. Now that boss might be pulled in through a "Boss" class of an "NPC" class of a "Character" class of a "Things" class. His behaviors might be tagged by a designer from a separate Behavioral AI library.

This might seem like it is being lazy, but remember that largely the limiting factor on huge projects is the complexity of the code. If you had to code the behavior of all of the monsters in your game one at a time without abstraction, you'll need to pare back the number tremendously. If you had to write the display code in assembly, you can forget about having an artist script a wispy smoke polygon shader effect. It would be much faster to hit the raw iron of your graphics card, but if you don't go through Direct X or Open GL you can forget about ever finishing.

So you optimize less, you create broader, slower code, and you get a lot more done. You get more game for your buck.

Is the code the most efficient ever? No. But that's not the point.

Re:Just as well...

[MyLongNickName]

May Heisenberg will protect us!

I have no idea what direction you are going with this. I have, however, determined exactly how fast you are going with this.

Re:Some miles are up hill and some are down hill..

[tomstdenis]

You need a stats class, badly.

No offense, but nothing is perfect. This is why we have a thing called "standard deviation".

Me hitting the letter "e" will probably not take the same amount of energy to process twice. But I bet over 1000 e's the standard deviation could be found and would indicate that 66% of the time it's "x J +/- y" and so on...

So you sample something like "building the linux kernel to a ram drive" 100 times, find the deviation and use that. The tighter AND lower the better. The wider and higher the worse.

Tom

News?

[tomstdenis]

I'd think both AMD and Intel are well aware of the MIPS/Watt challenge. It's not new. Problem is CUSTOMERS still want a bazillion Ghz attached to the processor because they think it will make it faster or better or something.

I've got two x85 class Opterons sitting here at 1Ghz most of the time. That's ~35W vs. ~95W. AMD seems to care about power. Intel is no worse off with the Pentium M and "core" series (netburst was a mistake).

Tom

What a day.

[fuzzyfozzie]

Dvorak admits he trolls, Chipmakers admit your power may be vary, what's next?
Looks like everyone's coming out of the closet today.

Re:What a day.

[Mark Maughan]

Pope admits...

Re:We have a nation of SUV's

[tomstdenis]

Because they're stupid. Then they bitch at the bank for the 1.50$ "service fee".

Let's see... processor running full steam instead of low power mode when idling probably amounts for a waste time of more than 90% (unless you work/live at the box).

Opteron at full == 95W, at low == 35W, diff 60W. price per KWh is about 7 to 10 cents. Let's say 8.5 to be close to middle. 60W * 24 * 31 * 0.085 = $3.80 per month. Probably double that once you factor in power supply inefficiencies and cooling costs. So you spend ~8$ per month because idling the box is "too hard". But $1.50 at the bank is robbery. ... hmmm ... Now tact on a bunch of other needless things like gas guzzling cars, retarded cable, etc... Each on their own is trivial to expense, but together you're spending hundreds of month stupidly... /rant...

Besides, multiply your wasted 44.7KWh per month by the millions of other people. That results in higher demand which raises the price. The price goes into other things like the cost of producing things that require electricity. So because people like you are apathetic and think "me being wasteful is ok" you end up paying more at the gas pumps and the stores for everything you touch.

Tom

I would like to know...

[Garabito]

Why, for a given chip, power consumption raises with clock speed? I know there's corelation, but I'd like to know the physical relation between the two variables.

Re:I would like to know...

[tomstdenis]

It has to do with the capacitance of the traces and the inefficiencies of the transistors themselves.

Raise the clock and the charge time on the traces goes down, means you need a higher voltage. Think of filling a bottle with a small hose. If you want to fill a single bottle faster you have to increase the pressure [voltage]. Also raises the current overall if you keep it up. This is why overclockers often have to raise the voltage of the part they are OC'ing.

Raise the clock and more transistors are switching per second. Switching generates heat because you have two inputs and one output [among other reasons]. The energy can't just disappear and you can't keep increasing the current otherwise the traces melt. Fortunately the energy is turned into heat ... which then invariably melts the chip hehehe...

Now, if you ran a circuit at twice the clock but did the same amount of work and shut it off at T=0.5 would you still use more power? [homework question].

Tom

Re:I would like to know...

[wkitchen]

Why, for a given chip, power consumption raises with clock speed? I know there's corelation, but I'd like to know the physical relation between the two variables.

When not changing state, a CMOS device dissipates almost no power. But each CMOS gate has a tiny capacitance that must be charged or discharged each time it changes state. This requires energy. The energy dissipated for each transition is essentially constant, but the number of transitions in a given time can vary. Since power=energy/time, the more transitions per unit of time, the more power is required and the more heat is generated.

Re:The Solution

[Dorceon]

Optimized for what pipeline length? The wrong one for the competition's processor?