Some motherboards had so called overclocking AI feature, which had predefined fail-safe working frequency and voltage settings for some unlocked CPUs. In which standard is stock setting, while turbo and extreme settings increased the values by 20-30%. Enabling extreme or turbo modes also disabled some power saving features(such as speed step) and automatically turned fans to higher RPMs. I had it in the bios of my previous rig which had Asus motherboard, but it didn't work as my CPU was overclocking locked. So far I know, this setting increased the FSB as well as multiplier. As the FSB was before not just reference clock, the frequencies of RAM and their voltage and timings were also altered.
But I didn't see it in any of the newer UEFI Bios motherboards.