📅 June 22, 2018
So, you purchased a brand new Ryzen 5 2600 3.4Ghz processor only to discover that Linux reports its speed as 1550 MHz. Why? Can it be fixed?
It turns out that that newer motherboards (X470, for example) for Ryzen CPUs include extra features. One feature is called PSS Support, and it needs to be disabled when using Linux in order for Linux to show the 3400 MHz CPU speed rating.
At first, I thought something was wrong. I had a new Ryzen 5 2600 CPU @ 3.4 GHz to experiment with, but HardInfo and /proc/cpuinfo both showed its clock speed as 1550 MHz (1.55 GHz) while BIOS showed 3400 MHz (3.4 Ghz).
Xubuntu 18.04 also demonstrated the same lower CPU speed.
What went wrong?
It turns out that something called PSS Support needs to be disabled in order for Linux to report the correct speed. Boot the system into BIOS, and it should be located under Advanced > CPU Configuration > PSS Support or somewhere similar.
In my case, Linux did not report the correct speed until PSS Support was disabled. Updating the kernel from 4.10.0 to something newer (4.16.17) did not help.
“What is PSS Support?”
Actually, I have almost no idea, and information is scarce. After scouring online, I encountered three definitions related to computers:
- Product Support Services – A business unit involving partner requests. (This cannot be right in this case.)
- Product Support Services – A Windows preinstallation environment
- Something that will “Enable/disable the generation of ACPI_PPC, _PSS, and _PST objects” as stated in the BIOS itself.
Apparently, it is not a common term, and the motherboard’s user manual gave no explanation. (I think the motherboard manufacturer expects end users to know.) Given that ACPI (Advanced Configuration and Power Interface) is mentioned, this might be tied to power management features and determines how to make the Ryzen more efficient based upon load.
I saw absolutely no difference in performance whether enabled or disabled, so I left it disabled. The system booted and shutdown normally. No crashes, slowdowns, or other abnomalities.
“Did it help?”
Yes. HardInfo and /proc/cpuinfo both report the correct 3400 MHz (3.4 GHz) that the processor should be running at.
The odd part is that Linux Mint 18.3 as shown in the screenshot above reported the same clock frequency for each core, but Xubuntu 18.04 always showed a slightly different clock speed for each core, and the core speeds would change each time cat /proc/cpuinfo executed.
“Did it make the computer run faster?”
I do not know because I cannot tell a difference. Despite the 3400 MHz speed being reported, benchmarks and everyday tasks run in the same amount of time. HardInfo benchmarks are barely any faster, and command line programs, such as compressing files, take the same amount of time with 3400 MHz as they did with the 1550 MHz rating before disabling PSS Support.
At this point, I am not sure. This six-core Ryzen 5 2600 seems hardly any faster than a five-year-old quad-core i7-4770. Perhaps there is another issue to resolve. Maybe this did not fix the issue at all but, instead, caused a different number to appear while keeping CPU performance the same. Time will tell.
Was this a failed experiment? Absolutely not!
This is what makes computers fun. Using a new processor is more than plugging it into a socket and affixing a heat sink. It often involves unexpected scenarios, such as this one, and then requires time, research, and experimentation to learn something new!