AComputerNovice-1376834 :
When first purchasing a computer, is default, factory BIOS settings the same? Is the BIOS default settings the same as the first purchased(factory) BIOS settings? Is there such a thing as a custom settings for a desktop when first bought to not be the same settings as default?
I'm not really sure what you're asking. I think that you may be confused by terminology. Don't fret though, there's a lot of confusion surrounding PC firmware that has resulted from decades of misnomers. I'll try and explain it in the simplest terms that I can.
The term BIOS stands for Basic Input Output System. It is a firmware standard originally designed by IBM for the IBM compatible PC and for use with Intel x86 microprocessors. BIOS is a firmware standard, not a particular piece of code itself. It specifies what the firmware must do, must not do, and what data structures it must follow. It does not specify
how the firmware should perform the tasks set out in the BIOS specification.
The purpose of having a firmware specification is two fold.
First, it sets up the PC in a platform specific fashion so that the operating system doesn't have to. The firmware for a motherboard is specific to that single motherboard. This is because the firmware for that motherboard has to initialize, configure, and test all of the components that the motherboard manufacturer has installed on that board. This is why operating systems do not have to have special code paths for Asus motherboards, Gigabyte motherboards, MSI motherboards, Supermicro motherboards, etc... Each motherboard employs firmware which is compliant with a common firmware specification, and the operating system takes advantage of that commonality to simplify its own tasks.
Second, it locates and loads the operating system's boot loader into memory, and then passes execution control to the boot loader. x86 microprocessors are entirely clueless about attached storage devices. On its own, a CPU wouldn't have any idea how to find a hard disk much less read from it. That task is handled by a series of other devices, including a memory controller and a storage controller. Intel's own PCH storage controller is by far the most commonly used one world wide, but add-in RAID controllers from LSI, Dell, HP, and others are also used. The firmware code instructs the CPU on how to find and initialize these storage devices, and then seeks out a bootable partition.
So that's a lot about BIOS, but what about other firmware standards? In the late 1990s, SGI released a series of workstations based around Intel's x86 microprocessors, but constructed them in such a fashion that they were not IBM PC compatible, and they did not use BIOS compliant firmware. Instead, SGI used their own ARCS firmware specification. More recently, the BIOS firmware standard has been replaced on the PC with the UEFI firmware standard. UEFI is much newer and does away with many of the constraints that made BIOS difficult and unruly after 30 years of use.
So where is the firmware stored and what's the deal with settings? Firmware is typically stored on a byte addressable storage device that is easily accessed without an intermediary controller. The firmware code is typically stored on a small EEPROM or a Flash ROM chip that's tied directly to the chipset and is easily accessed directly through the memory controller. When the system firmware is updated (colloquially called a BIOS update, even if that's a total misnomer), the contents of the EEPROM or Flash ROM are overwritten by the programmer. In case the term ROM is foreign to you, it stands for Read Only Memory. For reasons that are obvious, EEPROMs and Flash ROMs can be overwritten, but they are not designed to be overwritten repeatedly and usually require specific configuration to do so. Firmware settings that are configured by the user are typically stored elsewhere, historically in a volatile SRAM chip (sometimes called the CMOS, but again, this is a misnomer; a more appropriate term would be CMOS RAM), or more recently in non-volatile flash memory alongside the firmware code itself. Volatile means that the contents are not persistent; when the chip loses power, the contents are lost. Power to the volatile SRAM chip is provided either from the power supply when the motherboard is powered, or from the small button battery located on the motherboard.
The default values for the firmware are stored in the firmware itself on the EEPROM. During its execution, it checks the values in the aforementioned firmware memory to see if they mismatch or override the default values. If they do, they are applied.
I hope that this answered your question
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