The cooling system and the factors that affect the final frequency

The cooling system and the factors that affect the final frequency

Ryzen processors of any generation are very sensitive to temperature. The Zen 2 was no exception, but rather a challenge for those with weak cooling systems. I hope many of you remember the huge number of discussions on how to increase boost Ryzen processors in default mode. Just over a year ago, the guys from Gamers Nexus had a compelling experiment in which the boost processor was monitored at certain temperatures.

As you can see, the difference between 60 degrees and 85 is more than 200 MHz for the load on all cores. By the standards of modern processors, this is a serious value. So why is it happening?

First of all, the heat dissipation relative to the area has increased significantly.  For example, the AMD Ryzen 7 2700X produces a heat flux of 0.68 W/mm², while the AMD Ryzen 7 3800X already produces 1.21 W/mm². This is due to a finer silicon process, the size of the crystals is smaller and the heat release remains unchanged.

Secondly, a rise in the temperature of silicon affects the current consumption, which in turn affects the heat output of the processor. That is, we have a chain reaction in which the temperature of the processor causes the user to raise the operating voltage -> thus additional self-heating of the silicon occurs and the system again wants more voltage. Fortunately, this chain reaction is limited, but as a result at a certain frequency, the processor will want a significant voltage boost to conquer the next 25 MHz. Example. You have a processor accelerated to 4400 MHz at 1.25 V, you want to try to get a 4425 MHz and for this, you raise the voltage by 25 mV but the system remains unstable. You add another 25mV and then another 25mV. In the end, you get the coveted 25MHz by raising the operating voltage from 1.25V to 1.325V. That sounds awful, doesn't it? That's why CTR doesn't automatically recommend voltages above 1.25V. First of all, the CTR project is to achieve maximum performance with adequate power consumption.

I would also like to pay attention to the updated Ryzen processors with XT suffix, which, according to AMD company, have an "improved" technological process. In simple language, the Ryzen 9 3900XT, Ryzen 7 3800XT, and Ryzen 9 3900XT processors are based on silicon with High SIDD. The feature of these processors is to achieve higher frequencies at the same voltage. As a demonstration, I want to share the results of the comparative acceleration of the 3900X and 3900XT:

The updated processors do show higher frequencies, but they are often warmed up slightly more at the same voltage (by at least 5%). 

In order to minimize the impact of negative effects on silicon, custom water cooling should be used (this is very important for users of 3800X processors and older). By water cooling, I don't mean AIO because in most cases this product is no better than conventional air cooling. To prepare the CTR project, not only the most common AIO with clogged micro-channels was used, but also several types of custom cooling. In particular, a water block from the German company TechN was responsible for providing highly efficient cooling.

The product has a record density and depth of micro-channels, which certainly has a positive effect on heat dissipation, but the flow resistance increases.

To compensate for this, TechN engineers improved the input channel structure. Unlike other companies' water blocks, water enters the microchannels at a special angle to minimize resistance.

Another important feature of the water block is the shift of the inlet flow from the center. Since the CCD of Zen2 (and Zen3) is slightly off-center, this optimization will also improve heat dissipation.

The cold plate and mounting system also have a feature. During installation, the radius of curvature of the cold plate will change, and contact with the IHS (in a simple language "processor cover") processor will improve.

Often, such products are born in the hands of enthusiasts who want to break the market silence and improve something. In this case, lively competition contributes to the reduction of prices for products. The TechN block is no exception and I will soon introduce users to it in a big comparative test, but it will be separate material.

All in all. Competently selected cooling will give us additional performance. In particular, if you choose a water block it must be optimized for the CCD layout otherwise the cooling efficiency will decrease. A temperature range of 65 degrees is optimal, it does not cause serious chain reactions due to the self-heating of silicon. And this is just the beginning because the crystals of future processors will be reduced in size with constant power consumption.