Linux host, Windows and Linux guests: CPU does not exceed 1.99GHz

[JN]

Host: ThinkPad X1 Carbon 6th Generation. Intel i7-8550U (quad-core, plus hyperthreading giving eight virtual cores), 1.8GHz boosting to 4.0GHz. OS (natie) Linux Mint 19 x64 Cinnamon. The boost works on the native OS. When running Windows 10 Home in a VM, or Linux Mint 19.1 x64 Beta in a VM, the CPU speed in the guest does not exceed 1.99GHz. This severely limits performance.

Virtual Box 5.2.23 (test build). In each of the two VMs in question, four processors are allocated and the execution cap is set to 100 (one hundred)%.

[JN]

Compare these forum reports:

[1] ​https://forums.virtualbox.org/viewtopic.php?f=6&t=3993 [2] ​https://forums.virtualbox.org/viewtopic.php?f=6&t=54515

I can add that I get the CPU speed from within the Windows guest using the Windows Task Manager (performance tab) and from within the Linux guest by running:

watch -n1 "lscpu | grep 'MHz' | awk '{print $1}'"