One of the prominent parts of Intel’s announcement this week for the new 9th Generation core processors was that both the overclockable consumer processors and the new high-end desktop processors all feature a soldered thermal interface material (STIM) between the silicon die and the heatspreader. This is a vast improvement over the previous thermal interface material due to the solder's superior ability to conduct thermal energy away from the silicon die. As part of the announcement, Intel also engaged in some extreme overclocking at its launch event using Liquid Nitrogen as an effective coolant, and some overclocking world champions.

Choosing A Thermal Interface Material (TIM)

With the desktop processors we use today, they are built from a silicon die (the smart bit), a package substrate (the green bit), a heatspreader (the silver bit), and a material that helps transfer heat from the silicon die to the heatspreader. The quality of the binding between the silicon die and the heatspreader using this thermal interface material is a key component in the processors ability to remove the heat generated from using it.

Traditionally there are two different types of thermal material: a heat conductive paste, or a bonded metal. Both have positives and negatives.

Image from EKWB

The heat conductive paste is a universal tool – it can be applied to practically any manufactured processor, and is able to deal with a wide range of changing conditions. Because metals expand under temperature, when a processor is used and gets hot, it expands – so does the heatspreader. The paste can easily deal with this. This allows paste-based processors to live longer and in more environments. Using a bonded metal typically reduces the level of thermal cycling possible, as the metal also expands and contracts in a non-fluid way. This might mean the processors has a rated lifespan of several years, rather than a dozen years. However, the bonded metal solution performs a lot, lot better – metal conducts heat better than the silicon-based pastes – but it is slightly more expensive (a dollar or two per unit, at most, when the materials and manufacturing are taken into account).

Ryzen Delidded

Thermal Interface
Intel Celeron Pentium Core i3 Core i5 Core i7
Core i9
Sandy Bridge LGA1155 Paste Paste Paste Bonded Bonded Bonded
Ivy Bridge LGA1155 Paste Paste Paste Paste Paste Bonded
Haswell / DK LGA1150 Paste Paste Paste Paste Paste Bonded
Broadwell LGA1150 Paste Paste Paste Paste Paste Bonded
Skylake LGA1151 Paste Paste Paste Paste Paste Paste
Kaby Lake LGA1151 Paste Paste Paste Paste Paste -
Coffee Lake 1151 v2 Paste Paste Paste Paste Paste -
CFL-R 1151 v2 ? ? ? K = Bonded -
Zambezi AM3+ Bonded Carrizo AM4 Bonded
Vishera AM3+ Bonded Bristol R AM4 Bonded
Llano FM1 Paste Summit R AM4 Bonded
Trinity FM2 Paste Raven R AM4 Paste
Richland FM2 Paste Pinnacle AM4 Bonded
Kaveri FM2+ Paste / Bonded* TR TR4 Bonded
Carrizo FM2+ Paste TR2 TR4 Bonded
Kabini AM1 Paste      
*Some Kaveri Refresh were bonded

In our Ryzen APU delidding article, we went through the process of removing the heatspreader and conductive paste from a popular low cost product, and we showed that replacing that paste with a bonded liquid metal improved temperatures, overclocking, and performance in mid-range overclocks. If any company wants to make enthusiasts happy, using a bonded metal is the way to go.

Intel on Enthusiasts

For several years, Intel has always stated that they are there for enthusiasts. In the distant past, as the table above shows, Intel provided processors with a soldered bonded metal interface and was happy to do so. In recent times however, the whole product line was pushed into the heat conductive paste for a number of reasons.

Slide for Intel's 4th Gen, which used paste

As Intel was continually saying that they still cared about enthusiasts, a number of users were concerned that Intel was getting itself confused. Some believed that Intel had ‘enthusiasts’ and ‘overclockers’ in two distinct non-overlapping categories. It is what it is, but now Intel has returned to using applying STIM and wants to court overclockers again.

Pushing Frequencies with Liquid Nitrogen

I should be safe in saying that most AnandTech readers understand that in order to push an overclock, bigger and better cooling is required. This might mean a good air cooler, water cooling, or if you want an exotic daily system, chilled water. The idea here is that as the voltage and frequency is raised, more exotic cooling is required to keep the system from overheating. Beyond chilled water, there are a bunch of enthusiasts that use sub-zero coolants.

Competitive overclocking is an industry to which I am relatively intimate: I have at some point in my existence hit #2 in the world rankings, albeit briefly. The nature of the extreme overclocking scene has changed from very motivated enthusiasts and engineers to vendor backed individuals with thousands of dollars in hardware trying to get the very highest frequency, or break particular benchmark world records. It comes down to experience, preparation, and a good amount of luck to get the best hardware and the best results in the world.

For example, the high-frequency world record on an AMD processor is 8794.33 MHz, using a FX-8350 under liquid nitrogen, whereas the Intel record is 8532.17 MHz on a Celeron 352. Each processor runs differently when you get down to -196C, and some of the older processors were better at pushing the envelope. But while newer processors might not clock as high, the additional cores and raw per-MHz performance help push the benchmarking part of the world records higher.

So while a good air overclock on a high-end gaming processor like the Core i7-8086K is around 5.4 GHz, under liquid nitrogen Intel’s hired guns on the day were pushing 6.9 GHz with the latest 9th generation Core i9-9900K on all cores, and reaching 7.1 GHz internally, with up to 7.4 GHz on a single core. Given that the chip is new, there are usually a good couple of months of learning a new platform and chip binning to push it as high as the previous generation, so we’re likely to see higher over the coming months.

The two overclockers hired by Intel, known in the community as Splave and Steponz, were happily breaking records for 8-core processors left right and center for various CPU focused tests. They also achieved at least one ‘global’ world record, beating every other processor that has ever existed, in PCMark 10.

For a few other tests, Intel achieved some best ever 8-core results.

What’s the point?

Not everyone is going to run liquid nitrogen on their system. Not only is the cooling setup a disaster to maintain 24/7, as well as expensive, the inherent instability in the system at this frequency and the tuning required isn’t practical as it requires constant tweaking. Extreme overclocking is often compared to drag racing – to see who can go the quickest quarter mile. There are several parallels – going for the highest frequency might be just a peak speed contest, while running a complex benchmark is more akin to Formula 1. There are users that have been competitive overclocking for decades, and for a select few, it has become a career that has ended up with motherboards that offer new features that everyone who wants to can use. Sure, it isn’t as useful as taking a family saloon to the shops, but it is fun to watch them go.


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  • Oxford Guy - Monday, October 15, 2018 - link

    "What professional uses liquid nitrogen to cool a processor?"

    Professional enthusiasts.
  • AntonErtl - Saturday, October 13, 2018 - link

    About CPU lifetimes: The only CPU that I ever have seen failing was the Core i7 6700K (with paste) that failed after one year of use (with maybe 2 hours of overclocking during that time). By contrast, the Clawhammer Athlon 64 3200+ that I bought 15 years ago (with solder AFAIK) still works and is still in use.
  • Elstar - Tuesday, October 16, 2018 - link

    One thing I never understood about overclocking is why Intel or AMD doesn't try to make *more* money from the community on it. For example, given that very few CPUs can hit the highest frequencies, why not sell those that do at auction? I'm really curious what the market would pay for overclocked CPUs that are supported by Intel/AMD.
  • monglerbongler - Saturday, October 27, 2018 - link

    Is there any justification beyond theatrics for using liquid nitrogen vs dry ice acetone?

    In both systems, the temperature of the coolant is already far lower than the processor would require to function properly if it were in thermal equilibrium (eg at the same temperature) -78 C (~195 K) or -196 C (77k)

    However, Dry ice possesses a significantly higher (latent) enthalpy of sublimation compared with the (latent) heat of vaporization of liquid nitrogen (570 vs 200 kJ/kg). Furthermore, Dry ice is denser than liquid nitrogen (~1.4-1.6 kg/m^3 vs ~0.8 kg/m^3).

    In both cases, the heat sink is not the material itself storing the heat in excitations of vibrations/translations/rotations of atoms or molecules. Instead the heat is powering a phase change ("breaking" those intramolecular or intraatomic bonds). With liquid nitrogen, the material is already saturated with heat. Every gram of liquid nitrogen is in a constant process of vaporization (boiling). Same with dry ice, which is subliming.

    With dry ice/acetone you get 2x the heat sink (570 vs 200 kj/kg) and 2x the density (~1.5 vs ~0.8 kg/m^3). Its obviously not 1:1 because you can't pack the dry ice perfectly into the volume of the dewar heat sink, but its close. You can certainly smash up the dry ice with an ice pick and pack in there tightly.

    In theory you should be able to get significantly more than 2x the heat into the dry ice acetone bath than the liquid nitrogen. The safety consideration is minimal. In both cases you need ventilation so that concern would already be met. nitrogen for accidental asphixiation, and with dry ice acetone for the spark/fume hazard. However, the flammability and inhalation hazard is minimal with dry ice acetone as the vapor pressure is considerably lowered due to the lower temperature. This distinction is well known in the sciences. When scientists need a quick, simple, readily accessible, and most importantly CHEAP cooling method they use dry ice acetone.

    Go into any biology, chemistry, or materials science laboratory. Less well funded laboratories often utilize dry ice acetone to cool rotary evaporators and chemical reactions (because acetone is cheap and dry ice is readily available and provided by the facility, vs chillers which are expensive).
    Liquid nitrogen is also used, although its typically used when the temperature, rather than the heat dissipation, is the concern (eg lyophilization in a biochemistry setting or degassing in a chemistry/materials science setting).

    Dry ice is cheap. You can buy it at most grocery stores. You do not need a dewar. Acetone is cheap. You can buy it at 100% of hardware stores (either explicitly as "acetone" or in some cases as laquer thinner, although you should look up the SDS to make sure its not a different chemical or mixture) and most pharmacies (pure acetone nailpolish remover; you have to look at the label, as plenty of nailpolish removers have other chemicals added to them, but they definitely sell it)

    You can also use methanol, but that is more inherently toxic.

    So I ask again:

    Aside from theatrics.... the cool factor..... the NPC/NORP "like WOAH DUDE TOTALLY!" factor.... is there any justification for liquid nitrogen?

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