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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mino - Friday, December 15, 2006 - link
Read some paper on entropy.The problem in this discussion is most participants do not know what heat, electricity, work(i.e. in joule), work(i.e. inlogical one) means.
Except for electromagnetic waves that leak badly shielded PC and the energy required to transfer the information out of the PC (by monitor and network cables) the energy(in form of electricity) consumed by the CP is completely changed to heat.
In other words "focused" form of energy witch low entropy(electricity) is distributed to the environment and becomes an "unfocused" form of enegry, mostly heat. Also even the heat dispersed to the room is still partly focused in sense it still not spread to the whole universe.
Hope this clears it for some.
mino - Friday, December 15, 2006 - link
CP == PCsmitty3268 - Thursday, December 14, 2006 - link
I don't particularly know how transistors work (only the basics) but if a space heater isn't 100% efficient then why would a cpu be?Again, I could be wrong, but do you have any 3rd party info to support your claim?
Missing Ghost - Thursday, December 14, 2006 - link
I think space heaters are 100% efficient, except maybe if there is a fan, then it could be 99.999%.smitty3268 - Thursday, December 14, 2006 - link
If you can see something glowing, then at least part of the energy is producing visible light and not heat. Although now that you mention it, I think I heard that plain old light bulbs are fairly efficient heaters.smitty3268 - Thursday, December 14, 2006 - link
From http://www.intel.com/technology/silicon/si11031.ht...">http://www.intel.com/technology/silicon/si11031.ht...This implies what I was saying, but perhaps the devices only run cooler because they require less power to begin with?
JarredWalton - Thursday, December 14, 2006 - link
Heat density: less power in a smaller area can potentially run hotter (witness Prescott vs. Northwood P4). Except we're seeing the reverse here, so probably it's just a difference in chip/package design. There's no guarantee that the various chips are measured identically, meaning AMD could have changed temperature reporting with 65nm, and certainly the AMD vs. Intel numbers are not a direct comparison. I would put more weight on power numbers, personally.eRacer - Wednesday, December 20, 2006 - link
In future Brisbane reviews could you check the Brisbane idle temperature to see if it appears to be somewhat accurate? Other previews and leaks show Brisbane idle temperatures in the 10C-15C range which is well below room temperature. Idle and load temps of Brisbane may actually be 15C higher than what is reported.Stereodude - Thursday, December 14, 2006 - link
I was excluding the C2D from my comments. Sorry if that wasn't clear.If anything the die shrink should make the Brisbane run slightly hotter since the die is a little smaller. I can't come up with any good reason why one 65W processor runs cooler than another 65W processor given the same cooler and same size heat spreader. Maybe the heatspreaders aren't flat between all the AMD CPUs. The 35W AM2 processor definitely should have run cooler.
eRacer - Thursday, December 14, 2006 - link
"As you can expect, AMD is pricing the 65nm chips in line with its 90nm offerings to encourage the transition. Die size and TDP have both gone down to 147 mm^2 and 65W across the line.Is 147 mm^2 accurate? That happens to be the same die size of 90-nm A64 X2 Manchester, and isn't much of a shrink from the current 183mm^2 512KBx2 Windsor cores. Some rumors had put it at ~125 mm^2.