AMD recently posted in their community blog some additional information regarding Ryzen processors and how they handle a couple of things including Windows Power Options and the Temperature reporting. In the blog post, AMD addresses concerns regarding Thread Scheduling, temp reporting and Power Options.
As it has been a hotly, no pun intended, debated topic. We’ll highlight temp reporting here and as AMD goes on to mention, the Ryzen 1700X and 1800X both feature a 20*C offset on its readings to compensate for fan policy uniformity across the product line. AMD advises users to subtract 20*C off their temp reading to know what their junction temperature is. AMD also confirms in this post that the temperature sensor on the Ryzen processors are located in the junction, the interface between the die and heatspreader.
The primary temperature reporting sensor of the AMD Ryzen™ processor is a sensor called “T Control,” or tCTL for short. The tCTL sensor is derived from the junction (Tj) temperature—the interface point between the die and heatspreader—but it may be offset on certain CPU models so that all models on the AM4 Platform have the same maximum tCTL value. This approach ensures that all AMD Ryzen™ processors have a consistent fan policy.
Specifically, the AMD Ryzen™ 7 1700X and 1800X carry a +20°C offset between the tCTL° (reported) temperature and the actual Tj° temperature. In the short term, users of the AMD Ryzen™ 1700X and 1800X can simply subtract 20°C to determine the true junction temperature of their processor. No arithmetic is required for the Ryzen 7 1700. Long term, we expect temperature monitoring software to better understand our tCTL offsets to report the junction temperature automatically.
The table below serves as an example of how the tCTL sensor can be interpreted in a hypothetical scenario where a Ryzen processor is operating at 38°C.
|Product Name||True Junction Temp (Example)||tCTL Offset for Fan Policy
||Temp Reported by tCTL
|AMD Ryzen™ 7 1800X||38°C||20°C||58°C|
|AMD Ryzen™ 7 1700X||38°C||20°C||58°C|
|AMD Ryzen™ 7 1700||38°C||0°C||38°C|