amd ryzen 5950x max frequency is 3400MHz on ubuntu 20.04

Solution 1:

When you run the computer with heavy load, you get a boost value.

p-i@pi-TUF-Gaming-B550M:~$ lscpu
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   48 bits physical, 48 bits virtual
CPU(s):                          12
On-line CPU(s) list:             0-11
Thread(s) per core:              2
Core(s) per socket:              6
Socket(s):                       1
NUMA node(s):                    1
Vendor ID:                       AuthenticAMD
CPU family:                      25
Model:                           33
Model name:                      AMD Ryzen 5 5600X 6-Core Processor
Stepping:                        0
Frequency boost:                 enabled
CPU MHz:                         4418.048
CPU max MHz:                     3700,0000
CPU min MHz:                     2200,0000
BogoMIPS:                        7399.78

There is more information about Frequency boost on this page https://www.kernel.org/doc/Documentation/cpu-freq/boost.txt To enable Frequency boost you have to do a setting in BIOS. On my motherboard this setting is in AMD CBS and called Core Performance Boost.