With the specification of Thermal Design Power (TDP), most users have been connecting the maximum power consumption of processors for years. In the meantime, every manufacturer, whether with graphics cards or processors, has freed himself from freedoms, so the TDP can no longer be equated with the maximum power consumption.
AMD makes it clear that the TDP is to be understood as an indication for the cooler manufacturers who interpret their cooling concept. However, the TDP at these points is dependent on several factors, which are not communicated so publicly. And AMD now gives here a TDP specification of 95 and 65 watts for the three new CPUs, but also shows the following formula:
TDP (Watts) = (tCase ° C - tAmbient ° C) / (HSF Θca)
The tCase stands for the processor temperature, tAmbient represents the housing temperature, and HSF Θca is to be rated as a minimum temperature per watt for the cooler. AMD specifies this value with 0.189 and shows the following calculation example for the Ryzen 7 1800X:
(60-42) / 0.189 = 95.23 W TDP
AMD considers the 60 ° C as the optimal temperature for the CPU, for which, for example, XFR can still contribute to the performance increase, and 42 ° C as an optimal housing temperature and comes via this formula to the new TDP specification.
However, this no longer means that the processor does not require a higher electrical power consumption for itself. In the following, AMD makes it clear that there is a limit for the electrical power consumption for the AM4 socket and this is at 128 watts. The Ryzen 7 1800X is able to reach this limit with strong multi-core loads.
Thus, the understanding of the TDP today is absolutely different than before, although the TDP was also previously used as a guideline for the cooler manufacturers. The comparison of the TDP in our table above, in which the FX-8350 is called with 125 watts and Ryzen 7 1800X with 95 watts, is thus no longer directly comparable, because the FX-8350 had a maximum power consumption of 125 watts, the FX-9590 of 220 watts. Ryzen 7 1800X is a 128-watt and not a 95-watt CPU.
However, one must also keep - as we have already pointed out in the last articles - that Intel's top models are also beyond the scope of their power consumption with regard to TDP naming. According to our measurements, an Intel Core i7-6950X is rather a 197-watt CPU, instead of a 140-watt CPU.
Back to the R7 1800X: From the AMD declarations and the naming to the limit, however, it is also clear that here, apparently, protective mechanisms are set, and when countermeasures are taken. We know from a colleague that the CPU was reached when reaching about 125 watts throttle, thus clock and voltage were withdrawn.
