AMD's 65nm Brisbane Core Previewed: The most energy efficient AMD CPU to date
by Anand Lal Shimpi on December 14, 2006 6:08 PM EST- Posted in
- CPUs
Temperature, Overclocking and Final Words
Lower power consumption and cooler operation are both positive side effects of AMD's new 65nm process, the latter of which is exemplified by the graph below:
What we're looking at here is the core temperature of the 2nd core in all of the CPUs, under full load, as reported by Core Temp. While it's not necessarily useful (or accurate) to compare readings across two different motherboards, as is the case when looking at AMD vs. Intel, the comparisons between AMD chips alone are enough to showcase the reduction in temperature.
With both cores under load for 15 minutes (calculating Fast Fourier Transforms) the 65nm 5000+ manages to produce just about as much heat as the X2 3800+ EE SFF. While this won't always be the case, it gives you an idea of the reduction in temperatures you can expect from AMD's new 65nm chips.
What about overclockability? We were unfortunately not able to get that much more out of the new 65nm core as we could from mature 90nm chips. Our X2 5000+ was able to run at 2.925GHz, at 1.475V with stock air cooling. If equipped with better air cooling or something more exotic, reaching over 3GHz shouldn't be a problem, but we wouldn't expect to see anything too far over 3GHz.
Overall we're left with mixed feelings after playing with AMD's first 65nm chips. Power consumption is definitely reduced compared to its 90nm offerings; in our tests we saw an average reduction in total system power consumption of 14.6W thanks to the new Brisbane core. Along with the lower power draw comes lower temperatures, which is also good. For no additional cost, and given that it should help alleviate AMD's capacity constraints thanks to a smaller die, there's nothing to complain about on that front.
However we would like to see more, and we have a feeling that it may end up being the 2nd rev of 65nm CPUs from AMD that truly interest us. Just as we saw with AMD's 90nm cores, it wouldn't be too surprising to see lower TDP parts emerge as AMD's process matures. We do hope to see an Energy Efficient line of X2s built on AMD's 65nm process, although it may take some time for AMD's manufacturing to reach the point where it can offer significantly reduced TDP 65nm parts.
The tweaks and advancements that AMD can do to make its 65nm parts more attractive can only go so far; while they will boast lower power consumption and improve production numbers for AMD, what we really need is a long overdue update to the K8 architecture. AMD has already promised it and we're expecting big things by the middle of next year, but in the mean time at least things will be a little cooler on the green side.
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Live - Thursday, December 14, 2006 - link
It does not use more power then any other chip except the 90nm X2 5000+. Where did you get that from? Did you read the article?Stereodude - Thursday, December 14, 2006 - link
Yes, I read the article. Excluding the C2D it uses the 2nd most amount of power, basically tied with the 65W 4600+.smitty3268 - Thursday, December 14, 2006 - link
Not all the power that goes into a chip is released as heat. The heat is basically wasted power that "leaks." So if a chip can get more useful work out of the same amount of power then the amount of heat released would decrease even while power consumption remained steady.I'm not an expert, but I believe a lot of the special new process techniques we always here about (like strained silicon) basically just reduce the amount of wasted energy. Am I right here?
Stereodude - Thursday, December 14, 2006 - link
Sorry, but that's incorrect. All the power is turned into heat. The power can't be going anywhere else. Power in = Power out.It's not like a LED where you get some energy out as light, or a motor where you get mechanical energy out of it in addition to heat.
finalfan - Thursday, December 14, 2006 - link
If all the power can be turned into heat then it will be the most efficient heater the human being ever built. And even greater, you get all the computation done for free. Could you believe that?Stereodude - Thursday, December 14, 2006 - link
Where else is the energy going if it isn't getting turned into heat? You apparently don't have any idea how the transistors in a processor work.splines - Thursday, December 14, 2006 - link
You apparently don't have any idea about basic thermodynamics.If the processor released all of its energy in heat, it'd be the world's most efficient space heater.
You have forgotten a few little points, like that work is done by a processor (wouldn't be much point otherwise). Transistors are switched, mostly, however the IC itself can expand and contract, as well as the packaging material. The heat generated by a CPU is because of the resistance inherent to the circuits. All of the above is considered energy expended (or, more properly, changed in state).
In other words, don't go around insulting people's intelligence when you don't know yourself what you're on about.
Stereodude - Thursday, December 14, 2006 - link
I'm betting only one of us has an Electrical Engineering degree, and guess what... You're not the one with it.The work being done by the CPU is what makes the heat. The transistors themselves create heat because they consume power, and a lot of it, to switch from one state to another at high speeds.
I will say it again since you still don't get it, though it probably won't help. Energy is conserved. Electrical energy goes in, and heat comes out. The thermal expansion and contraction of the part isn't work. It's a side effect of the heat being product when the transistors consume electrical power by switching and make heat.
slayerized - Friday, December 15, 2006 - link
Thermodynamics 101- First law of thermodynamics: “Energy can neither be created nor destroyed, it can only be converted from one form to another” (Power --> Heat)smitty3268 - Friday, December 15, 2006 - link
I think everyone here knows that, the issue is that current -> heat is not the only type of transformation that can occur. If it was then anything electric wouldn't be able to do anything at all except create heat, and obviously that isn't true.