Intel Sandy Bridge-E Core i7-3960X CPU Review

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Power Consumption / Temperature Testing

Power Consumption / Temperature Testing

Power Consumption

For this section, every energy saving feature was enabled in the respective BIOSes and the Windows 7 power plan was changed from High Performance to Balanced.

For our idle test, we let the system idle for 15 minutes and measured the peak wattage through our UPM EM100 power meter.

For our CPU load test, we ran Prime95 v26.6 64-bit In-place large FFTs on all available threads for 15 minutes, measuring the peak wattage via the UPM EM100 power meter.

For our overall system load test, we ran Prime95 v26.6 64-bit In-place large FFTs on all available threads for 15 minutes, while simultaneously loading the GPU with OCCT v3.1.0 GPU:OCCT stress test at 1680x1050@60Hz in full screen mode.

At face value, the Core i7-3960X has high power consumption, it’s the second most gluttonous processor on our chart. However, that obviously doesn’t tell the true tale, since unlike Bulldozer , Sandy Bridge-E’s monstrous performance actually justifies its power consumption. The i7-3960X is about 50% faster than the FX-8150 in multi-threaded workloads, yet only consumes 12 watts more. It does not consume much less than a Core i7-980X, but you are getting about 10-25% higher performance across the board, with vastly improved idle results. Compared to mainstream quad-core Sandy Bridge, power consumption is up by 60% but multi-threaded performance gains are above 50%. Overall then, the Core i7-3960X’s performance-per-watt is actually quite excellent.

Having said all that, we can’t help but wonder the extent to which those disabled cores and L3 cache are contributing to the consumption figure. If they are fully power-gated it should be very little, but there is no way for us to tell at this moment.

Temperature Testing

For the temperature testing, we used the Intel Thermal Solution RTS2011LC liquid cooler. The ambient temperature was 23°C/73.4°F. The application used to monitor temperatures was AIDA64 v1.85.1719 beta Keep in mind that the thermal sensors in most modern processors are not really accurate at measuring idle temperatures, hence the very small delta between the room temp and the idle results.

Idle: The system was left to idle for 15 minutes.
Load: Prime 95 In-place large FFTs was run for 15 minutes.

Since we don’t yet have a compatible LGA2011 bracket for our Thermalright Ultra-120 eXtreme or Prolimatech Mega Shadow heatsinks it’s hard for us to compare the i7-3960X’s heat output to other processors that we have tested. However, based on these results we can tell you that our sample was not a particularly hot-running chip, certainly nothing like the infamous early Core i7D0 LGA1366's.

The Thermal Solution RTS2011LC proved to be an exceptionally quiet-running cooler, with the fan nearly always running at a silent 878RPM. In auto mode, we saw it peak at 958RPM a few times when the system was fully loaded for 15 minutes, but obviously even that was inaudible. We actually had to go in the bios to set 100% fan speed to get the above results. At that level, the fan spins at 2200 RPM, pushes about 73CFM, and outputs roughly 35 dBA. It’s definitely not a terrible product, but it will be interesting to see how much it actually retails for and performs when compared to similar units from Antec, Cooler Master, Corsair, etc. We think a high-end heatsink with a 1600RPM 120mm fan might just outperform it, albeit with greater noise levels.

 

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Overclocking Results

Overclocking Results

As Intel revealed at IDF 2011, Sandy Bridge-E has a lot of overclocking potential. In fact, they were proudly showing off systems running at 5Ghz with all core and threads enabled using the Thermal Solution RTS2011LC liquid cooler. Let's see if our luck is as good.

Once again we haven’t had the opportunity to spend too much time overclocking on this new platform, but so far things are looking very positive. The above overclock was achieved with a little over 1.45V, and it seemed relatively stable so far in general purpose apps. Full stability will likely be 200-300MHz lower. We will update this page with our highest stable CPU, bus, memory overclocks a little later on. On a side note, you will all be glad to hear that when you overclock SB-E, power consumption does not shoot upwards like a rocket. The increase is much more linear and normal.

Overclocking on Sandy Bridge-E is very similar to mainstream Sandy Bridge, except for the fact that it’s generally better in every way. There is more bus speed headroom, the memory overclocking is drastically improved, and there is the awesome new Gear Ratio feature that acts as an additional master multiplier for both the processor and memory. First, the Gear Ratio (or Reference Gear Ratio / Host Clock Multiplier) comes in three flavours: 1.00, 1.25X, and 1.66X. How you use it is simple. Let’s say you are using a 40X CPU multiplier, 100MHz bus speed, and your memory is running at DDR3-1600. If you switch the Gear Ratio from 1.00X to 1.25X, your processor overclock will jump from 4.0GHz to 5.0GHz, your memory speed will increase from DDR3-1600 to DDR3-2000, and your bus speed will stay at 100MHz. So you can achieve a huge overclock without having changed the CPU multiplier, memory multiplier, or bus speed. As a result, even the i7-3820, which is ‘partially locked’ and has 45X CPU multiplier cap, will be able to hit some otherworldly clock speeds. Our only slight disappointment is that the memory dividers are still in large 266MHz increments, but we will have to wait for Ivy Bridge before this situation is changed.

 

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Conclusion

Conclusion

Speaking broadly, Sandy Bridge-E is everything that we expected. Up until now power users have had to compromise and choose between the Sandy Bridge’s superlative lightly-threaded performance and Gulftown’s unmatched multi-threaded performance. The Core i7-3960X features the best of both worlds, and then some. It combines the overall clock-per-clock advantage of the Sandy Bridge cores with six-core/twelve-threads of multi-threading crunching power.

As we stated in the Gulftown review, this is a specialized processor insofar as you need software that supports more than eight threads to really take advantage of its true potential, which is hard to find right now in the consumer realm. There are still only small handful of games that can make use of more than 4 threads, and even those that can don’t actually gain any additional performance, they merely spread a smaller load across all the cores. Having said all that, if you are considering spending $1000-$1600 to upgrade to the LGA2011 platform you probably know your usage needs better than we do.

Starting with the i7-980X, it’s a clean sweep across the board for the i7-3960X. No surprises there. Both chips have the same numbers of cores and threads, but the SB-E processor is based on the much faster Sandy Bridge microarchitecture. Having said that, Gulftown chips are no slouch. Yes, they are starting to show their age when it comes to lightly-threaded performance, but in highly multi-threaded workloads our i7-980X 'only' lagged by 10-25%. That is not insignificant, but it might not be worth the cost of upgrading just yet.

With regard to the i7-2600K, in single-threaded applications the performance differences are minimal and can be attributed to the clock speed difference between the two chips. As we demonstrated earlier in our clock-per-clock showdown, there really isn’t any difference between Sandy Bridge and Sandy Bridge-E when it comes to lightly-threaded workloads. However, multi-threading is obviously where the i7-3960X shines. With 50% more cores than mainstream Sandy Bridge, SB-E performs roughly 50% better in applications that make proper use of all those threads. When it comes to gaming, and particularly with regard to most modern games, LGA2011’s extra cores don’t really come into play. Only in the most CPU-centric games like those based on Valve’s Source engine can we really see some noticeably gains, but they are few and far between. Once PCI-E 3.0 graphics cards are released things might just skew heavily in LGA2011’s favour, but it is still too early to make any definitive statements.

What we can say definitively is that the LGA2011 platform is going to be unmatched if you’re planning on any triple or quad graphics card setups. With its 40 PCI-E lanes and newer, more efficient PCI-Express controller you will get better gaming results in multi-GPU configurations. NVIDIA has suggested that the gains can be in the 10-20% range depending on the resolution, so that’s quite significant and we are going to be putting those claims to the test shortly.

Next let’s move on to a topic that is now on everyone’s mind due to Bulldozer: power consumption. Now it might be shocking to hear, but our Sandy Bridge-E sample consumed a little bit more power than our Bulldozer chip. However, and this is the part that matters, the i7-3960X is about 50% faster than the FX-8150 in multi-threaded workloads. As a result, its performance-per-watt is actually quite excellent. It does not consume much less than a Core i7-980X, but you are getting about 10-25% higher performance across the board, with vastly improved idle results. Compared to mainstream quad-core Sandy Bridge, power consumption is up by 60% but multi-threaded performance is about 50% better. Considering how exceptionally power efficient LGA1155 processors are, this demonstrates to us that Intel have done a great job with SB-E.

Overall, what you have here is the platform with the best multi-threading performance, top-notch single-threaded performance, the most numbers of PCI-E lanes, future-proof PCI-Express 3.0 support, overclocking capabilities that should please even the most ardent enthusiast, and more than reasonable power consumption numbers. Let's be honest here though, the i7-3960X that we tested today might be fantastic, but it is not going to make or break this platform. It's the i7-3820 and i7-3930K that we are really excited about, and at least on paper they look like good deals. Yes, you are going to pay more for this platform, largely for the motherboard since as we demonstrated earlier you can simply re-use your current dual-channel kit without much of a performance hit, but if you want the best this is it. If class-leading multi-threaded performance and multi-GPU capabilities aren’t your priorities, and you have more down to earth requirements, then wait for Ivy Bridge.