Intel Core 2 on 45nm: Performance, Overclocking, Power Usage

CPU by piotke @ 2007-10-29

Intel is launching their successor the popular Conroe CPU, build on 45nm manufacturing process, it boasts reduced power consumption and has 50% more L2 cache. The first product out the door is a quad core beast dubbed QX9650. We take this new creation through its paces, comparing performance, power consumption and venturing into overclocking land, where sub zero cooling is the norm.

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Benchmarks - Multi Core

Benchmarks – Multi Core

The benchmarks were run on the QX9650 and E6850 with multi core enabled, this means though that benchmarks which benefit from the extra cores on the QX9650 you will see a large difference, but not all benchmarks support multiple cores, and thus the advantage of the QX is lost.

First up we compare the raw CPU performance with PiFast,SuperPi and Wprime:

Madshrimps (c)

PiFast and SuperPi take no advantage of the extra cores on the QX9650, but the extra L2 cache does pay off, SuperPi 1M improves by ~12%, 32M sees less effect, only ~3%; PiFast even less at only ~1%. Wprime does support multi core, the quick calculation of Wprime 32M is ~53% faster on the Quad Core QX9650, the longer Wprime 1024M also improves by the same amount.

Moving on the synthetic benchmarks of Sisoft Sandra 2008:

Madshrimps (c)

The multimedia tests more than double, the Multimedia Int improves by 135%! The Arithmetic tests are even more impressive, increasing up to 147%.

Madshrimps (c)

The Cinebench includes single core as well as multi core results, you can see that the QX9650 already has a small lead over the E6850 when both are using only 1 core, about ~10% better. The benchmark does not scale perfectly to the maximum amount of cores, otherwise the E6850 should be at 1000 and the QX9650 at 2000.

The x264 encoding test next:

Madshrimps (c)

The more cores the merrier, close to 100% increase at the 1st pass, and up to 123% faster on the 2nd pass.

Let’s take a look at the game benchmarks ->
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Comment from Sidney @ 2007/10/29
Reading other reviews, it would seem the engineering sample tested at [M] requires more vcore than others. 4Ghz quad would now be common speed; no bragging right unless you see 5Ghz.
Comment from jmke @ 2007/10/29
yes that seems to be the case, but no faulting engineering samples, they are supposed to run without fault at rated speeds with default vcore, which this QX9650 did
Comment from Kougar @ 2007/10/29
2.0v for 4.9GHz? Would have loved to see what that did to the power consumption figures for that CPU!

Regarding the discrepancy with your power chart, I think that has something to do with the physical properties of the chip design. I suspect that at very high frequencies there is a thermal threshold that once neared the leakage increases dramatically. After which it will quickly reach the point where the chip ceases to function or function stably since the increased leakage raises the heat, and the heat only further increases the transistor leakage in a self-fulfilling cycle. I don't have any real proof other than my own experiences with my Q6600...

I am curious, I notice from that CPUZ image the ES QX9650 uses 1.20v at 3GHz. My own Q6600 does the same... so how far can you drop the voltage and have the QX9650 remain stable at 3Ghz? I got a Q6600 down to 1.5v, but somewhere below that point my Q6600 will show errors. Gigabyte unfortunately lacks most of the FSB voltage tuning ASUS boards offer, as some members on the XS forums claim to have reached 1.10v for 2.5-2.8Ghz speeds for Kentsfields. Would be interesting to note what effect the smaller process size and change in transistor materials would have on this for Penryn.
Comment from jmke @ 2007/10/29
Originally Posted by Kougar View Post
2.0v for 4.9GHz? Would have loved to see what that did to the power consumption figures for that CPU!
You can last chart on this page: 36
386W vs 210W stock
Comment from Kougar @ 2007/10/30
Ah, nice! I had completely missed that, staring me in the face. I guess I need to take more power measurements since the data I have on my Q6600 includes my video card...

Why not extend that same chart a bit more to the right though, and undervolt that puppy?
Comment from CFKane @ 2007/10/30
I'm a little surprised that you're talking about a discrepancy in the chart while you're mentioning the changed cooling solution in the same sentence. The die temperature is one of the most important factors for the CPU power consumption and if you switch to a solution which removes the heat more efficiently, you should expect reduced power draw even with a higher clock and voltage.

That's also the reason why the maximum current in the electrical specifications for CPUs significantly exceeds what you would get from dividing the TDP by the core voltage. It's given for the maximum die temperature, which you will (hopefully) never reach in a real world situation.

Bear that in mind when testing or comparing CPU power consumption: The room/case temperature and cooling solution have a major influence and the die temperature at a certain load is an interesting figure to report along the power draw (sadly missing in most reviews).
Comment from jmke @ 2007/10/30
Thank you CFKane for you post and welcome to the forums
since the temperature was the only large difference between the two settings we were not doubting that it was indeed the lower temperature which was causing the lower temps; but I've not seen any article on the web discussing this aspect of the power consumption... hence were a bit hesitant to include that statement.
Comment from jmke @ 2007/12/07
we also got word back from Intel explaining the power usage at different temperatures:

Matty @ Intel:

Yes, the power consumption is reduced when the temperature of the processor is lowered.

There are many things that happen in a CPU when the temperature is changed and to elaborate further on the processor specific causes we have to look at the origin of the power consumption. We can divide the total consumed power into two main parts, static power (Ps) and dynamic power (Pd).

The static power consumption is what we usually call the leakage. In an ideal transistor, it should completely shut off the channel between the source-drain, gate-source and gate-drain. Transistors are far from ideal, and the current leaks between these parts and the substrate of the processor, and this is heavily dependent on the temperature.
For example, going from room temperature to 85C (~60C difference) increases the leakage power by a factor of more than 50. Thus, reducing the temperature with the same amount will make a huge impact on Ps.

Dynamic power consumption is emitted during the short amount of time that the transistor switches. Lower temperature reduces the resistance in the processor which results in shorter delay/faster switching of the transistors. Shorter delays and less noisy signals also reduce Pd.

I hope this explanation give you some clarity to the relation between power consumption and temperature. This can even be seen with air cooling: The power consumption is lower just after a load is applied compared to after a while when the temperature has levelled out, even though the load is the same.