I've read the reason why the Ryzen X processors over-report CPU die temperature by 20 degrees C.
OK, but at least let users optionally turn this off!
My mobo BIOS fan control is designed for a normal range of CPU temps. Having the sensor report 20 degC high means all ramp control is impossible - the best I can do is fans idle or full blast, and even moderate changes in system load will jump them between these states. I've seen others discuss this too.
So this Band-Aid for cooling actually causes a cooling problem and a major irritation. I now wish I hadn't bought an 'X' CPU - the performance boost isn't really worth the annoyance.
I run a Prime X370-PRO and using HWinfo my Tdie reports the actual temperature and Tctl has the +20 offset for fan control. In silent mode the radiator fans run at 200 rpm and slowly ramp up speed has temperature increases. I do admit that fan control in bios is not functioning properly but Asus AI suite is able to calibrate fans properly.
CPU: AMD R7 1700X
MBD: ASUS PRIME X370-PRO
> CPU = 50C
CPU AMDRyzen 7 1700X
> CPU (Tctl) = 63.8C
> CPU (Tdie) = 43.8C
ASUS PRIME X370-PRO
> CPU = 50C
ASUS AI Suite 3
> CPU = 50C
> CPU = 43.8C
The BIOS CPU temperature is the same as the ASUS AI Suite 3 CPU temperature.
The HWiNFO64 CPU (Tdie) temperature is the same as the Ryzen Master CPU temperature.
I am assuming that the temperatures shown in the BIOS and ASUS AI Suite 3 are CPU socket temperatures.
Note that these comparisons are not exact since each measurement may have a different update interval.
I have monitored and calibrated the fans with ASUS AI Suite 3. With it the fan speeds are set by the CPU socket temperature. That means the 20C offset plays no role in what speed the fans are running at.
I do not use the BIOS Q-Fan control so I can't comment on that.
OP here; sorry for the delay in responding.
I do have an Asus Crosshair VI mobo. I have not yet installed BIOS v1403, am still at 1201 I think. I will install 1403 especially if it has a fix for the 20 degC over-reporting (that is not completely clear from the responses). I didn't think the Asus BIOS team would ever address anything not OC-related, especially something AMD had specified for 'equipment protection'.
I'm sure that some Windows util can compensate for the 20C and control the fans, but I always rely on BIOS fan control. In particular I avoid Asus AI Suites; in 10 years of trying to make those work they've failed me every time. I won't even install it.
Thanks for the responses and links.