Any · Hardware

Know your BIOS settings (the 5 that matter)

Most of the speed potential in a PC is already there — it's locked in the BIOS/UEFI. Five settings unlock most of it.

Before you start

High risk. This change is reversible — you can return to the previous state without professional help or data loss.

Photograph each screen before you change anything. UEFI has no undo, and 'load optimised defaults' also throws away settings you wanted to keep.
One setting at a time, reboot in between. Change five at once and a machine that won't start tells you nothing about which one did it.
XMP/EXPO is an overclock, just a pre-packaged one. Not every kit hits its rated speed on every board — if the PC gets flaky after enabling it, that's the first thing to turn back off.
If it won't post at all, the fix is a CMOS clear, not the UEFI menu you can no longer reach: power off at the wall, then move the CLR_CMOS jumper or pull the board battery for a minute.
The names vary by manufacturer. Resizable BAR may appear as 'Above 4G Decoding' plus 'Re-Size BAR Support', and virtualisation is VT-x on Intel but SVM on AMD.

Enter UEFI (usually F2 / DEL at boot). XMP/EXPO: enable it or your RAM runs at 2133 MHz instead of its rated speed
Resizable BAR (Above 4G): on for GPU
C-States: off if you do low-latency work
Boot order: put your SSD first
Enable virtualisation (VT-x / SVM) only if you use VMs or Android emulators — off is safer otherwise

The PC boots normally, RAM runs at its rated speed (Task Manager → Memory), and the UEFI settings persist across reboots.

The PC fails to post or is unstable after a change — enter UEFI again and reset that setting (or load optimized defaults).

Next stop: the related fixes below, or start a guided diagnosis.