The latter can be necessary, because as soon as a critical threshold is triggered for a sensor, the baseband management controller (BMC) spins the fans up to full speed (as a safety measure).
So if your changes don’t have the desired effect and the fans run at full speed instead, then check the IPMI system event log (SEL) for critical events (see below).
IPMI management of a local system interface requires a compatible IPMI kernel driver to be installed and configured.
On Linux this driver is called Open IPMI and it is included in standard distributions.
Using a standardized interface and protocol allows systems-management software based on IPMI to manage multiple disparate servers.
For “other” chassis, Intel also provides three generic SDRs called slow, medium and fast ramp.