If you lot're looking for authoritative data on how much cooling is plenty for your CPU, y'all'll be difficult-pressed to find an answer. While nosotros all know that modern processors need some caste of active cooling, very fiddling official information exists to say how different temperatures bear upon a CPU's functioning.

Editor'southward Notation:
Matt Bach is the head of Puget Labs and has been part of Puget Systems, a boutique builder of gaming and workstation PCs, since the early on days. This commodity was originally published on the Puget blog.

Older CPUs would merely fail if they started to overheat, but modern CPUs adjust their frequency based on temperature (among other things) to forestall a dramatic failure. Because of this, it stands to reason that one time you reach certain temps, yous will no longer exist getting the maximum performance from your CPU because it will exist busy protecting itself.

But what is that temperature? And exercise yous actually need a high-end liquid-cooled system to get elevation performance, or is the picayune stock libation that comes with nearly CPUs plenty? In this article we volition respond these questions and more.

How CPUs should be affected by temperature

Modern CPUs are able to adjust their operating frequencies through a number of technologies in guild to either reduce their ability consumption or provide maximum power as needed. The start of these modern technologies is Turbo Boost (or Turbo Core for AMD APU/CPUs). According to the overview folio for Intel Turbo Heave Technology 2.0, there are five factors that affect the amount of increased frequency an Intel CPU tin can achieve via Turbo Boost:

  • Blazon of workload
  • Number of active cores
  • Estimated current consumption
  • Estimated power consumption
  • Processor temperature

For this article, processor temperature is the chief factor nosotros are concerned well-nigh. You would expect Turbo Heave to slowly stepping back the amount of Turbo Boost as the CPU gets hotter. In actuality, an Intel CPU under heavy load will actually run at the maximum Turbo Heave allowed by the other four factors until it hits the CPU's thermal limit.

CPUs also have extremely robust thermal protection. If the CPU starts operating above the CPU's thermal limit it will brainstorm to reduce the frequency in order to foreclose catastrophic failure. Oddly, we have found that the thermal limit for both Turbo Boost and thermal protection on Intel CPUs to be right at 100 °C - which makes it very convenient to remember. In other words, until the CPU hits 100 °C yous should see 100% of the CPU's available performance. Once you starting hitting 100 °C, nonetheless, the CPU will beginning throttling back to go along itself from overheating

How cooling really affects Intel CPU performance

Nosotros know from both feel and explicit testing that mod Intel CPUs (at the very least Sandy Bridge, Ivy Bridge, and Haswell) can run at their maximum Turbo Heave frequency all the way up to 100 °C. While in that location may be a tiny performance departure between a CPU running at 30 °C and one running at 95 °C, our testing has found that the difference is miniscule. In fact, even after running benchmarks dozens of times the difference is so small that it is substantially nonexistent.

What we can measure out is what happens once a CPU starts to hit 100 °C. To figure this out, we took an Intel Core i7 4790 and cooled it with a Gelid Silent Spirit Rev. 2 CPU cooler that was connected to a transmission PWM fan speed controller. Past running Linpack (which is a CPU benchmark widely used in the scientific community) and slowly dialing the fan speed down in careful increments, we were able to allow the CPU to overheat by incremental amounts. At each cooling increase we kept a log of the Linpack criterion results as well as using CoreTemp to record the CPU core temperature and frequency.

Since the Intel CPU thermal limit is 100 °C, we can quantify the corporeality of overheating by measuring the amount of fourth dimension the CPU temperature was running at > 99 °C.

We were very surprised when our testing showed that while the minimum CPU load frequency started to drop as soon as the CPU striking 100 °C, the average CPU frequency didn't drop by more than .1GHz until the CPU was overheating more than xxx% of the time. In fact, Intel CPUs are surprisingly good at being able to handle this much estrus with such a small reduction in the average frequency.

While this is a bully style to understand what is happening from a frequency standpoint, we wanted to know how this affects existent-globe performance. To do so, we recorded the Linpack performance results to see what the actual performance implications of overheating are:

Linpack is one of the most consistent CPU benchmarks we have ever seen and the Intel Core i7 4790 should score right at 190 GFlops with the problem size we used for this testing (30000). What is interesting is that the Linpack results from our testing well-nigh exactly follow the average CPU frequency from the previous graph. While information technology makes complete sense, this pretty much just confirms that from a strictly CPU functioning signal of view, the performance of a CPU is direct related to it'due south average frequency.

So what does this all hateful? Beyond the fact that Intel CPUs are impressively stable even while technically overheating it means that y'all can expect full performance from an Intel CPU as long equally you keep it below 100 °C. At the same fourth dimension, even if the CPU occasionally hits 100 °C you shouldn't see more than a minimal drop in performance until it spends a significant amount of fourth dimension (more than than 20% of the fourth dimension) above 99 °C.

Is stock cooling acceptable?

While the data from the previous section is really interesting, it may be hard to translate into a real world situation. To help with this, nosotros performed the exact same Linpack test except that instead of altering the cooling manually we used two different CPU coolers - the stock libation that came bundled with the Cadre i7 4790 and the budget-friendly Libation Chief Hyper TX3 which only costs most $20. To brand this every bit real-world as possible, we installed our test hardware (Asus Sabertooth Z97 Mark II, Intel Cadre i7 4790, 4x Kingston HyperX LoVo DDR3-1600 4GB, NVIDIA GeForce GTX 980) into a Fractal Pattern Define R4 chassis with the stock fans running at 5V.

As yous can meet from the graph above, even a very affordable CPU cooler like the CM Hyper TX3 is able to dramatically lower the CPU temperature under load. While the stock cooler is easily hitting 100 °C during the benchmark run, the CM Hyper TX3 only always hits a maximum temperature of 80 °C. In terms of how much the CPU was overheating, the stock cooler allowed the CPU to run at > 99 °C about 20% of the time.

According to our graphs from the previous section, we should expect a measurable, albeit pocket-sized, drib in performance with the stock cooler. We found that using the stock cooler made the CPU perform about 2.five% slower than it did with the CM Hyper TX3. The neat matter is that this drib in functioning almost exactly lines up with our graphs of expected performance from the previous section.

Conclusion

The results of our testing tin pretty much be summarized with the following three points:

  • Modern Intel CPUs run at full speed (including the full Turbo Boost immune based on the number of cores and workload) all the way upward to 100 °C
  • Even later the CPU hits 100 °C, the operation is not profoundly affected until the CPU spends virtually 20% of the time > 99 °C
  • While stock cooling only causes around a 2.v% drop in functioning, even a budget after marketplace libation will dramatically improve CPU temperatures

Frankly, we were a bit surprised at how well mod Intel CPUs dealt with really loftier temperatures. They manage to run at full speed all the style up to 100 °C, and fifty-fifty and then the performance is not profoundly affected unless they spend a significant amount of fourth dimension at that temperature. We certainly don't advocate letting your CPU run at those kinds of temperatures, however. While this article is about performance in that location are plenty of non-performance based reasons to keep your CPU temperature at a more than reasonable level.

Sensitive electronics like CPUs have a finite lifespan and running them at college temperatures shortens it. So unless you lot desire to take an alibi to upgrade your system often, higher temperatures are counter-productive.

With PC hardware, higher temperatures make both pocket-sized and major hardware faults much more likely. These hardware faults can effect in anything from reduced performance due to minor errors needing to be corrected to information abuse or bluescreens due to more dramatic errors.

The difficult thing is that just saying "lower temperatures are better" is an overly simplified fashion to look at CPU temperatures when y'all consider a PC every bit a whole. While you tin use giant liquid cooling loops, insanely high flow fans, or even things like liquid nitrogen to continue a CPU extremely well cooled those methods are either expensive, cumbersome, loud, or a combination of all three. In reality it is generally improve to allow the CPU run a little warm in lodge to properly remainder the cooling against the rut output of the CPU.

For example, the Corsair Hydro H60 is a great closed-loop CPU libation used on most of Puget's high wattage CPUs, but it would be overkill for a low-wattage Intel Cadre i3 CPU. It would certainly keep the CPU well cooled, but it would exist much louder, more complex (due to the liquid and pump), and more expensive than what is necessary. Instead, a CM Hyper TX3 or Gelid Tranquillo (if y'all want to have the system even quieter) would be a better match for that CPU even though the CPU would run slightly hotter under load.

For the average system, a rule of thumb at Puget Systems is that the CPU should run around 80-85 °C when put nether full load for an extended period of time. This gives the CPU plenty of thermal headroom, does not greatly impact the CPU'southward lifespan, and keeps the system rock stable without overdoing it on cooling. Lower temperatures are, of form, better (inside reason) simply if you desire a target to aim for, 80-85 °C is what we generally recommend.