Update: It turned out to be some errant whitespace. Once removed, I was able to patch the kernel and have the processor supported better.
Initially, I got this message
intel_idle: does not run on family 6 model 23
That has now changed to,
intel_idle: Please enable MWAIT in BIOS SETUP
The HP BIOS is very limited and does not expose such an option in the setup.
No driver is reported active, as was the case before applying the patch, however, the processor now appears to be running at 80%, as opposed to max.
Is there a way to activate acpi_idle instead?
Update: A microcode update, combined with adding
to my boot configuration, sorted out my specific issue