- raw, unshared access to devices.
- no more interrupts.
You can get really close to this via virtualization though.
Run a guest machine without operating system on the hypervisor. It doesn't even have to be low level code to get most of the benefits (for example MirageOS)
If the OS has no need to interrupt you, it will never interrupt you. The OS doesn't context switch from a usefully running application on its own core unless you ask it to.
