Also known as: BIOS, UEFI
BIOS (Basic Input/Output System) and its modern successor UEFI (Unified Extensible Firmware Interface) are the firmware that brings a computer’s hardware up at power-on and hands control to the operating system.12
Overview
Stored in a flash chip on the motherboard, this firmware is the very first code a CPU runs when power is applied. It performs the power-on self-test (POST), a quick sanity check of memory and core devices, then initializes the chipset, RAM, and basic peripherals so the machine is in a known, working state.
Once the platform is up, the firmware consults its configured boot order, locates a bootable storage device, and starts that device’s bootloader, which in turn loads the operating system. The firmware also exposes a setup screen for changing boot order, clocks, and virtualization toggles, and it can itself be updated — a process called flashing.
BIOS versus UEFI
Legacy BIOS dates to the original IBM PC of the early 1980s and carried real limitations by modern standards. UEFI replaced it with a cleaner, more capable design:
| Aspect | Legacy BIOS | UEFI |
|---|---|---|
| Era | Early 1980s | 2000s onward |
| Disk scheme | MBR (≤ 2 TB) | GPT (very large disks) |
| Mode | 16-bit real mode | 32-/64-bit |
| Boot integrity | None | Secure Boot |
| Interface | Text menus | Drivers, shell, richer UI |
Most systems shipped in the last decade use UEFI, often with a compatibility support module (CSM) that emulates legacy BIOS for older operating systems.
Where it fits
BIOS/UEFI is the indispensable layer between bare hardware and software — without it a machine has no idea how to start. On small SDR capture boards the role is filled by an equivalent bootloader or ROM baked into the platform rather than a PC-style setup screen, but the job is identical: wake the hardware, then start the OS that runs the GopherTrunk daemon.