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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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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.
I still have more fans than freaks. WTF is wrong with you people?
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So it's exactly like the miles-per-gallon on new cars.
"I use a Mac because I'm just better than you are."
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!
So how does the electric company know how much you've used if power is impossible to measure?
BTW, EPA mpg are measured without using real mile on real roads.
Engineering is the art of compromise.
Our nation is one of conviences, not of caring if our grandchildren have conviences.
May Heisenberg will protect us!
Stop! Dremel time!
Miles per gallon are hardly constant either. Uphill? Downhill? 10mph or 100? Highway or city? Same difference.
---- Den ene knappen er powerknapp, den andre er Bender voice knapp "Bite My Shiny Metal Ass"
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.
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
gets three libraries of congress per watt.
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
Someday, I'll have a real sig.
As long as my AMD 3200 heats my home in the winter, I'm mighty fine thanks.
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
Someday, I'll have a real sig.
Dvorak admits he trolls, Chipmakers admit your power may be vary, what's next?
Looks like everyone's coming out of the closet today.
The SUV of CPUs.
I don't want it to be like buying industrial lighting where you have to compare 60W bulbs with 800 lumens to 75W bulbs with 1000 lumens.
I'm not confused by simple linear ratios: We just don't need naming conventions and measurements whose only purpose is to obfuscate easy
comparisons that would allow for simple commodity pricing of a consumer good (which is what you are purchasing -- operations per second).
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.
It seems some want to eliminate the time component from speed measurements, so you'd only care that one machine got to 110,000 calculations versus another getting to 120,000 calculations.
With desktop machines, just hook up each computer to a 1000VA battery backup UPS and see how FAR each gets ... not whether one got to 100,000 calcs in six minutes versus twelve minutes.
At first glance, I thought the headline said "Chipmunks" instead of "Chipmakers." For a split second I thought maybe Alvin, Simon, and Theodore had a tech column going.
This sig, aah-ah, is comin' like a ghost-sig...
But now all of the sudden we are about MIPS per Watt. Wow, what a novel concept. Designing machines that don't waste power. That has never beend done. Of course it is all just an advertising scam. The measurements will be skewed to promote a particular vendor, and customers will be disappointed when the real world performance is different.
The problem is that a GPC will not be equally good at all tasks. So we should ask out what the primary function will be, and what the secondary functions will be, and what irrational constraints we have that will limit the choices. For instance, my laptop is pretty power conservative, and cool, for most application that I run. However,when I do heavy number crunching, it get hot and I make sure to plug it in.
The same will hold for most people. If you need a browser and email, a power sipper will do. If you need office application, you can probably sacrifice effeciency for more power. If you are going to crunch number, for instance animation, then all the power in the world doesn't matter. And if you just want a hummer, then get one and stop complaining that the thing costs $500 a month to run. Make your choice.
So nothing has really changed. Basing purchasing decision primarily on these artificial indications is still a silly thing to do. It is nice that manufacturers are finally admitting that perhaps their hardware is bloated, but what I want is real optimization, not just larger caches to fool certain benchmarks.
"She's a scientist and a lesbian. She's not going to let it slide." Orphan Black
This stuff will come along soon and save them. So don't worry, just keep consuming.
The same exact processor can exhibit up to 50% variation in average power usage. Manufacturing variability.
Then I want to know the next step. I want to know how many tens/hundreds/thousands/millions of instructions per cycle (I henceforth trademark the analogy GIPC/MIPC/KPC for any processor performance comparison!!!!) the processor can handle, plus the comparative cycle rate (I.E. Speed) of the processor. Then I'd compare that per watt. I'd think that would be better - specialized instructions or not.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
They just about guesstimate.
Just do a bunch of taxing stuff until it goes out.
My solution, that is:
A standardised code segment with broad instruction type usage and a long time to complete(to minimize differences/errors). If everybody is using the same reference instruction sequence on all processors for the same amount of time, no debate ensues. Right?
Why hasn't anyone combined the concepts of heat pipe, heat sink, and calorimeter? Anyone who's taken high school physics knows the concept.
The foundation's already there, in water cooling systems. A rudimentary system could be built by dropping a thermometer in the reservoir, and turning off the radiator at the beginning of each test.
Granted, you're only measuring waste heat, but how much power does a CPU pump through data busses?
tasks(723) drafts(105) languages(484) examples(29106)
I still feel deeply cheated by that company. They came out with a FREKIN AWESOME tech and screwd up in the marketing. They had a VLIW processor. They could have easily doubled the number of pipelines and been the performance king. they were already the power usage king to begin with. Along with specialised hardware support for task switching, syscalls etc. they could have dictated PC architecture and gien me my laptop which runs on battery for 10+ hours b/c the processor is only eating up 10 measley watts compared to its notmal 60-80 right now. BUT, what do they do. They forget appreances. Nobody was amazed be a super power efficient chip with the performance of the lowest power celeron. Normal people didn't even know about it. Buisnesses didn't care b/c transmeta had too little cash (and thus little backing) and gamers (the ones who could hae furnished all that extra money) didn't care b/c of crap performance. So now, we are stuck with slow and inefficient processors based on 30 year old architecture designs.
He had a point though; if you constantly do video editing with your PC, your personal measurements of performance will be different from someone who uses only Word and Firefox all the time.
... etc.
There's a reason I ask people what they intend to do with their PC before selling them one -- do they need more ram, or more drive space or more drives or a bigger video card
Very rarely does CPU speed come into the equation; the slowest CPU available at retail is quite fast enough for most people, most of the time, but if they say "Play 3D video games", it might not be.
- Michael T. Babcock (Yes, I blog)
The article glosses over the real problems.
The first real problem is that blade servers are so small now, but require so much power, that companies can easily fit way more compute power in a server room than can be reasonably cooled. So they need more power-efficient servers to use their server space effectively.
And the problem isn't that power can't be measured--it can be measured just as easily as performance. Which is the problem hinted at in the article--firms focusing on the positive results they have and pushing that way of measuring power. Which is what they've been doing with performance for decades. Everyone can measure power, but what "benchmark" should we use?
And to correct other comments, chip dynamic power utilization is proportional to fCV^2, where f=frequency, C=capacitance, V=voltage. Reducing a chip's frequency from 2GHz to 1.5GHz will only at best save you 25% of the power. But, circuit speed is also proportional to voltage, so if a chip at 1.2V can operate at 2GHz, there's a good chance it might operate at 1.5GHz at 1.0V (or maybe 1.1V). So the real power savings is in the voltage reduction: 1.2V at 2GHz use almost twice the power as at 1.0V at 1.5GHz. But chips waste power even at 0Hz, especially at 90nm and below, so it's not quite that good. I believe AMD and Intel both use voltage reduction to save power in their reduced power modes.
-----
Sig Sauer
Knowing Google's lust for data collection, the Soviet Union is still alive and well inside the psyche of Sergey Brin....
However, miles are miles, and gallons are gallons. There's no one simple way to measure processor performance
Cars are just as easy and just as hard to compare. For example, how do you compare a Viper's performance versus a Metro's? They explicitely picked miles per gallon, and the Metro is going to win that. Had they instead picked acceleration, the Metro looses. Do the same for processors then. Pick a test and use it. Define strict conditions and go by them. For example, you would get miles per gallon by driving, say 60 MPH down an empty highway with cruise control, not by just telling both drivers to meet you at the gas station and then checking the gas tanks when they get there. So, for the processor, pick a particular benchmark test, say CrystalMark (which, btw, does a nice blend of tests rather than just one -- here's a Google translation version: CrystalMark someone might want to cache that, it's kind of slow even before I post a link on Slashdot) and compare the chips while checking power usage. You don't have to make it needlessly complicated. If one test isn't good enough, use more than one test tool and come up with a rating system that blends the results appropriately. No need to make excuses...
Having the idea of maximizing efficiency is one thing, actually doing it is another. Transmeta chips were just too slow.
Why?
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...
But with different usage-patterns you *will* get consinstant differences..so sure, you'd get data, and they'd be valid, but that doesn't mean GP needs a stat-class. Regardless of how much people refuse to believe it, even in todays 'massage-the-data-until-you-find-something(anythin g-will-do)'-world, the ol' trusted "garbage in, garbage out" still holds.
"" How about taking the safety labels off everything, and let the stupidity-problem solve itself? """
I'm sorry, but under no conditions will "compile this C file" vary by an unmanageable amount. If you expect the power to vary by 500 Watts each time you compile something... you're sadly mistaken.
... you're wrong.
Most likely with the CPU/memory under full load the Wh deviation is less than 10% of the mean usage. On a typical desktop the Wh rating is about 200-250 at full load. If you see a variance of more than say +/- 20Wh something is wrong or the test isn't reproducible. If you think things like differing occurences of interrupts and cache misses will make a difference in Wattage
So if you can say box A and box B compile [or do work] in T units of time, let's compare the power. Box A takes 100Wh +/- 15Wh and box B takes 175Wh +/- 20Wh. Which one do you suppose takes more power? Is that "numbers-saying-anything-they-want?"
That's the whole MIPS/Watt thing. If AMD and Intel hit an empasse where both are just as IPC efficient the next question is the power they take to get there. Sure if Box A takes 3x the time the results need adjusting (namely it takes 3x the power) but we say MIPS PER WATT for a reason.
Tom
Someday, I'll have a real sig.
Why?
;-)
Because, as the parent post pointed out, the problem of how to describe the measurement of a varying quantity does not actually pose a problem.
But with different usage-patterns you *will* get consinstant differences.
I agree the "hitting E" example seems a bit odd, but I would guess the parent just needs a computer science course badly.
Instead, do the same with a few typical real-world usage patterns (arranged into a repeatable suite). Then divide the performance value by the watts value, and you have a ballpark measure of performance-per-watt. Repeat the test a few hundred times, and you can get the mean and standard deviation.
Now, your objection seems to center on the idea that not everyone will use a computer with a similar usage pattern. I grant that as true, almost trivially. But if you want a one-number rating, you need to accept some averaging.
Personally, as someone who writes his own CPU heavy code, I might only care about how efficiently it can process an inner loop of "movq, psllq, pxor, pand, paddd, movq, psrlq, pxor, pand, paddd" (a real example from a program I toyed with last year, which probably single-handedly accounted for over half of my main PC's CPU time for several months). But even having a highly unusual usage pattern, I still get numbers in the same ballpark as published benchmarks. Why? Because chipwide power consumption depends far more on architectural considerations than it does on individual instruction-with-context consumption.
Dropping to 90nm SOI gave AMD a huge leap over Intel when they introduced the Winchester core Athlon 64s - Then an additional boost with the "dual stress liner" Venice core. And now Intel has come back with the 25W Core Duo (The M, Yonah's predecessor, did better than the Athlon 64s, but cost an arm and a leg), which seems poised to take the crown of MIPS-per-watt for a while. And how did it do this? By further architectural changes such as the drop to 65nm and reduction in the number of FPU pipelines. So although it might have poor FP performance, the specific instruction mix won't matter as much as overall "FP-heavy"ness - And then, similarly FP-heavy apps will get similar MFLOPS-per-watt.
Flops are used to measure the number of "Floating Point Operations Per Second" (flops), why not "Float Point Operations Per Watt"? :D
Hall effect sensors can easily measure current with no resistance added or interfering with the circuit. Many IC manufacturers test VERY complex integrated systems every day with NO issues -- and IC test setups use nowhere near 1ohm for current tests. Maybe 0.1 ohm. I think the real problem here is the lack of a standardized setup and method for measuring. Having different supply points or loads on a single chip is pretty trivial. The biggest difference is the performance -- what the chip is doing -- when it is measured. I'd almost think you'd want a ramp up of processor performance and measure current use while this happens. There is no guarantee with todays processors that performace is linear with power consumption. Either that or measure at standard "benchmark" levels.
The God of Abraham, Isaac and Jacob is very cool and has all the power you can imagine and more. Only those who believe in him can avoid the eternal maximum thermal dissipation (also known as Hell).
Charge up a new battery, see how many mAh it has, and use the computer. See how long it lasts with the way you use a computer. There, that's the only number that really matters.
My God, it's Full of Source!
OUTSIDE_IP=$(dig +short my.ip @outsideip.net)
That’s not even true: for a start, a UK gallon is some 20% bigger than a US gallon, and there are many more types of gallon in existence...
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