Linus Torvalds Criticizes AMD fTPM for System Hangs and Calls for Its Disablement

In May 2020, Linus Torvalds announced his switch from Intel to an AMD Threadripper‑based workstation, noting a three‑fold speedup in his all‑modconfig kernel builds. This endorsement spurred many developers to adopt AMD platforms.

Three years later, Torvalds expressed strong dissatisfaction with AMD's firmware TPM (fTPM), urging the community to "disable the stupid fTPM hwrnd" due to severe system stutter.

TPM (Trusted Platform Module) is a hardware or firmware‑based security module required by Windows 11. Many AMD users enable fTPM in BIOS to meet this requirement, but reports surfaced of intermittent freezes, audio glitches, and frame‑rate drops on Ryzen systems.

AMD investigated and identified the root cause: certain Ryzen configurations execute extended memory transactions related to fTPM in the motherboard’s SPI flash, temporarily halting other memory accesses and causing the observed stalls.

AMD’s initial mitigation for Windows users was to recommend using a discrete hardware TPM (dTPM) instead of fTPM. While this improved Windows performance, Linux distributions continued to suffer, especially in kernel 6.1 where the issue manifested as severe compile‑time errors and random‑number‑generator (hwrng) failures.

Torvalds argued that fTPM should only be used during boot to seed the kernel’s entropy pool; during normal operation it should not serve as a random‑number source. He suggested disabling fTPM entirely and relying on the CPU’s rdrand instruction, which, although slower, incurs only a few hundred CPU cycles compared to the multi‑second stalls caused by fTPM.

He warned that disabling fTPM may limit certain security features, such as hardware‑based encryption, but considered it a preferable trade‑off until AMD provides a robust fix.