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fir

cores and energy

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As far as I know those days 8-core amd procesors are avaliable on the market (not sure i I am not mistaken somethink I have weak orientation in hardware) Would like to buy one better than 4-core, why not, but the thing that worries me is energy. Does not 8 core cpu uses near 8 times more energy than one core? does it will multiply with the yet increasing core sizes? If I read opinions that after a couple of years we will have 60- core procesors or some years l8er 1000-core systems I doubt it because of such energy question - w ho would like to run 10kiloWat machine at home :/ 

(not me ;/ i would like to have at most 200W system, the better yet 100W)

Edited by fir

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If your only goal is to get a processor with low power usage, there is such a thing for that.  

 

Intel's latest chipset, the Haswell family, includes low-watt processors designed for tablets and other fan-less portable computers. It has 28W and 15W varieites, and even a 4.5W 2-core processing-limited chip.

 

If you are going for the high-end 4770K chip, the max power is 84W. If you think about the number-crunching abilities it has when running at full power and compare it to the history of computing, that power usage is pretty low.

 

On most game-related computers it is the video card that sucks down power.  The GTX690 draws up to 300W, the GTX590 used up to 365W.  

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If your only goal is to get a processor with low power usage, there is such a thing for that.  

 

Intel's latest chipset, the Haswell family, includes low-watt processors designed for tablets and other fan-less portable computers. It has 28W and 15W varieites, and even a 4.5W 2-core processing-limited chip.

 

If you are going for the high-end 4770K chip, the max power is 84W. If you think about the number-crunching abilities it has when running at full power and compare it to the history of computing, that power usage is pretty low.

 

On most game-related computers it is the video card that sucks down power.  The GTX690 draws up to 300W, the GTX590 used up to 365W.  

 

are multicore processor times more consuming in energy or can this be reduced magically, and how? this is importnt question to know

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are multicore processor times more consuming in energy or can this be reduced magically, and how? this is importnt question to know


They use dynamic frequency scaling and other techniques so they don't run at full speed all the time and so save energy/generate less heat/etc. The only time they run at full power is if you give them lot of stuff to do.

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are multicore processor times more consuming in energy or can this be reduced magically, and how? this is importnt question to know


Power consumption does not necessarily scale linearly with the number of cores. For instance there are many parts that are shared between cores. Also, unused cores will consume much less power, like a single core CPU will consume less power if it does nothing.

Your best bet is to look at the specs of the specific CPUs you have in mind. It should least peak, minimum and average power consumption.

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The fabrication process affects the size of the components (transistors), which affects the power requirements.

If you simply copied an old core design, fabricated in the same way but with 8 of them next to each other, then yes, power usage might go up by ~8x (disregarding variable frequencies, shared components, etc).
But if you redesign the chip with components that are 1/8th the size that they used to be, then power usage might even go down ;)

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Circuits on VLSI have two main sources of power consumption:  dynamic and static power dissipation.  Dynamic power has already largely been described in this topic.  It is the result of the circuit toggling in response to demand from "code" that you're running.  The main formula that governs this power consumption is:  P = 0.5 CV2f

 

C = total switched capacitance

V = voltage

f = frequency

 

As you can see power consumption is most affected by voltage as it increases with its square.  The singular most effective way to control dynamic power is to reduce voltage.  But when you reduce voltage the operating circuit will no longer be able to perform at its maximum frequency, thus frequency must be reduced.  Someone already mentioned it earler, but this is how dynamic frequency scaling works.  A table is created with voltage indexes into frequency.  The underlying OS will request a frequency and/or voltage and the hardware will automatically adjust.

 

The other component to power consumption is static power dissipation, otherwise known as leakage current.  Leakage current is undesirable current that performs no useful function (typically although research is being done into operating at ultra-low frequencies with leakage power).  Even if you turn off an individual transistor it still is conducting current.  In older technologies (> 65nm feature size) this power consumption was negligible.  In modern devices the total power consumed approach 30-50% of the total power used!

 

Leakage power manifests from fundamental quantum theory.  Electrons literally teleport across an insulating barrier in an effect known as tunneling.  More tunneling is done the smaller devices become.

 

There's more to learn if you're interested.  For "plug-into-the-wall" PCs / servers power consumption is less of a concern.  Although end-users (server farms, etc.) are looking to reduce their power footprint because it is becoming a major operational cost.  For handhelds intelligent circuit design is used to control voltage and frequency:  dynamic frequency scaling, automatic voltage scaling, temperature based clocked throttling (so your IC doesn't melt), instruction based clock throttling (high power assembly code will trigger power dampening), et. al. 

 

I keep getting the feeling that aside from standard benchmarks which show frequency and voltage, there should also be requirements for temperature.

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If you simply copied an old core design, fabricated in the same way but with 8 of them next to each other, then yes, power usage might go up by ~8x (disregarding variable frequencies, shared components, etc).
But if you redesign the chip with components that are 1/8th the size that they used to be, then power usage might even go down ;)
Let's put it in real-world data. It's easy to do that with AMD chips since their architecture basically stayed the same for years!
  • AMD Athlon 3000+: clocked at 2400Mhz (core Venice), 90nm. Launched april 2005. 89W
  • AMD Athlon ][ 450: 3 cores at 3200Mhz (roughtly equivalent to 4Ghz Venice), 45nm SOI. Launched October 2009. 95W

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If you simply copied an old core design, fabricated in the same way but with 8 of them next to each other, then yes, power usage might go up by ~8x (disregarding variable frequencies, shared components, etc).
But if you redesign the chip with components that are 1/8th the size that they used to be, then power usage might even go down ;)
Let's put it in real-world data. It's easy to do that with AMD chips since their architecture basically stayed the same for years!
  • AMD Athlon 3000+: clocked at 2400Mhz (core Venice), 90nm. Launched april 2005. 89W
  • AMD Athlon ][ 450: 3 cores at 3200Mhz (roughtly equivalent to 4Ghz Venice), 45nm SOI. Launched October 2009. 95W

 

 

ok, if so it seem that maybe multicore systems with low power consumption are possible - i was not sure as to that

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Not only possible, but the power (computing) per power (energy) ratio is generally better in multi-core machines, according to Intel. In other words, multiple cores do the same work using less power.

 

Note that the 8-core AMD machines that you mentioned earlier are really 6-core machines that show 8 cores, much like Intel processors did with hyperthreading for decades. It's kind of cheating, but most of the time this somehow maximizes the processor resource usage without impairing speed in a noticeable manner (usually, not all processor units are active at the same time).

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Note that the 8-core AMD machines that you mentioned earlier are really 4-core machines that show 8 cores, something like some Intel processors did with hyperthreading for about a decade.
I feel like making those notes.

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Not only possible, but the power (computing) per power (energy) ratio is generally better in multi-core machines, according to Intel. In other words, multiple cores do the same work using less power.

 

Note that the 8-core AMD machines that you mentioned earlier are really 6-core machines that show 8 cores, much like Intel processors did with hyperthreading for decades. It's kind of cheating, but most of the time this somehow maximizes the processor resource usage without impairing speed in a noticeable manner (usually, not all processor units are active at the same time).

 

it is not quite as intel did with hyperthreading, the AMD "8 core" CPUs have 4 modules where each module has 2 integer units, 2 128bit FMAC(can be unified to a single 256bit unit for one of the "cores"), 2x64KB 2-way L1 data cache. so for integer operations and 128bit SIMD instructions it is essentially a 8 core CPU

each module however shares a 16KB 4 way L1 instruction cache, a L2 cache and a FPU as well as the whole instruction fetch,decode,dispatch system and the branch predictor. so for floating point operations or 256bit SIMD it is a 4 core CPU with something similar to hyperthreading.

Edited by SimonForsman

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Are you trying to choose the CPU for laptop? Because otherwise 50W difference between AMD and Intel CPU is just irrelevant.

 

There are other cases too.

Right now I'm building a fan-less desktop computer for my father, those Haswell processors seem pretty neat.

35W instead of 85W will make a huge difference for that.

Quad Core i5 at 2,9GHz should be plenty for all his photoshopping needs I think, pretty amazing it doesn't need more power then half a light bulb :)

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Quad Core i5 at 2,9GHz should be plenty for all his photoshopping needs I think, pretty amazing it doesn't need more power then half a light bulb

Depends on the lightbulb you use. Around here the old-style 100W incandescents are nearly impossible to come by. Most of the bulbs in my house are 9W LED bulbs.

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Right now I'm building a fan-less desktop computer for my father, those Haswell processors seem pretty neat.
35W instead of 85W will make a huge difference for that.

They don't look pretty neat to me. I've been running my 95W Athlon X3 above fanless for years about now. I am always surprised how easy Intel CPUs go hot even at base load albeit they don't at peak. What to see it with your eyes?

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They don't look pretty neat to me. I've been running my 95W Athlon X3 above fanless for years about now. I am always surprised how easy Intel CPUs go hot even at base load albeit they don't at peak. What to see it with your eyes?

 

You must use some big heatsinks to dissipate 95W... watercooling? Or are you living in cold climate?

 

I'm planning to use a pretty small box (mITX, Streacom FC8) for it.

The box is actually rated by the manufacturer to support cpu:s up to 95W, but I don't believe them.

In a test I read, they ran it at 60W with OK temp, so I'm figuring it will run cool at 35W. (with long life and no problems even on hot summer days)

 

Unfortunately, dad liked the old silver one better then the upgraded black one, so I think its a good idea to go low on the wattage.

Since he doesn't play any games, I won't even put an extra graphics card in. 

The HD 4600 should be plenty for his needs, and anyhow, only a GT610 would fit in the box.. but mostly be just 60W of unnecessary power.

 

And hey, its good for the environment ;)

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No watercooling and no cold climate. But big sink yes, payed it 30. It sure wouldn't fit a box pc.

Talking about environment? Buy a new fridge. New water pumps. Desktop CPUs are not part of the picture if you're serious about that.

If he does'n play games, you would buy him a Celeron.

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Talking about environment? Buy a new fridge. New water pumps. Desktop CPUs are not part of the picture if you're serious about that.

 

I was hoping the smiley on the end of that line would indicate how serious I was... :)

compact and silent is the goals.

 


If he does'n play games, you would buy him a Celeron.

 

What would the advantage of a celeron be?

As far as I can see, the least power consuming celeron is at 35W too, but then with only 2 cores and lower clock.

Seems I get more bang for the watt with i5 haswell.

Price isn't that big of a deal, and I'd like it if he could use the computer for at least the next 5 years.

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