Slow HP Elitebook 840 laptop ?

I currently use an employer issued HP Elitebook 840 G4-laptop for development work. It has annoyed me. It has bothered me. It has always been totally under-performing, despite its Intel Core i7 CPU, and even with power connected and all Windows power management settings verified to be sane. I didn’t figure out why until recently ..

As it turns out, the laptop has unfortune default BIOS-settings coupled with a power supply that is probably too weak. At a glance, all the important settings look ok: CPU turbo boost enabled, multi-core, hyper threading and virtualization enabled, runtime power management enabled. But there is another option that turns out to be extremely important for performance. It’s buried under “Built-in device options”, and it’s called “Boost Converter”. Off by default. There is no explanation in the BIOS itself about what this option does. (Hello, hardware vendors: how difficult can it be to provide a one sentence explanation for ALL the settings ?)

Eventually I found a PDF document online that explains various HP BIOS options. And it describes “Boost Converter” as:

Draws power from the battery to give the CPU a momentary performance gain.

http://h10032.www1.hp.com/ctg/Manual/c03481740

Check ! Enabled. And the laptop suddenly becomes much more powerful when connected to A/C power. Because now, CPU turbo boost actually works. Instead of maxing out at 2,8GHz core speed, it now happily jumps up to 3,8GHz when needed. (There is also a BIOS option to enable turbo boost when only running on battery power, but I left that off.)

I now enjoy more fan noise, in addition to faster software builds, faster Docker containers and a faster IntelliJ. And in case you wondered, the battery still charges, even though it us used for extra power in addition to A/C when needed.