Most enthusiasts know that a PC's CPU will turn down to avoid overheating. GPUs and even most PCIe 50. SSDs ship with heavy heatsinks and blowers. But the latest victim of thermal throttling may be the PCI Express bus itself – which is being programmed to slow down the link or shut down some of its lanes.

It's an eyebrow-raising scenario that suggests a new driver from Intel. Phronics, who is overseeing the development of Intel's PCI Express driver for Linux, noted that the latest modification allows limiting the speed of the PCI Express link in case of thermal stress. The keyword is “bwctrl”.

This suggests that even a properly cooled GPU or SSD may not be able to access as much data as it normally would because the PCI Express link itself will slow down. Even worse, there's the possibility that drivers can automatically shut down some PCIe lanes when needed, to keep everything cool. In other words, a PCI Express x16 connection can go down to a slow speed, then start closing the lane – turning it into an x8 connection.

gave Notes Kernel.org notes that the latter won't be possible until PCI Express 6.0, however – although that's not far off.

“This series adds a PCIe bandwidth controller (bwctrl) and associated PCIe cooling driver to the thermal core side to limit PCIe link speed due to thermal reasons,” Intel engineer Ilpo Järvinen wrote. “PCIe Bandwidth Controller is a PCI Express Bus port service driver. A cooling device is created for each port that the service driver looks for if it supports variable speed. This series only supports PCIe link speed control. Controlling the PCIe Link Width can also be useful but AFAIK, there is no mechanism for this until PCIe 6.0 (L0p) so link width throttling is not included through this series. “

PCI Express 6.0 was the specification. Announced in 2022.The hardware is yet to arrive though. (That should be soon, however, as PCI-SIG originally predicted devices would begin supporting the specification in March 2024.) Currently, Intel is focusing on its cooling solutions with servers in mind. Looking.

But There are PCIe 5 SSDs.and that in advance Requires a dedicated cooler. It's not too hard to believe that PCIe 6 will require even more aggressive cooling, and PCI Express bandwidth throttling and link width control can be an unfortunate side effect under extreme conditions.