I installed Fedora 28 and Archlinux onto my development machine; a Lenovo Thinkpad t470s. Generally both distributions ran perfectly fine, but I did run into a problem on battery power. On battery power my CPUs would not go over 800 Mhz. By plugging in the laptop the CPUs would spin up to their usual 3 Ghz rating.
Then I found this archlinux power management throttling article Lenovo_ThinkPad_X1_Carbon_(Gen_6)#Power_management.2FThrottling_issues. Exactly what I was seeing, but on the t470s.
I installed msr-tools and modprobed the module:
pacman -S msr-tools modprobe msr
Then ran the wrmsr utility to set the CPU registers manually:
wrmsr -a 0x1a2 0x3000000 # which sets the offset to 3 C, so the new trip point is 97 C
While on battery power, the CPUs are scaling to their correct clock frequencies. I suspect this might be a bios issue, since it is happening on the X1 Carbon and the t470s.