I'm studying for the ISC2 Certified Cloud Security Professional (CCSP) exam and part of the course curriculum discusses BIOS. At one point, the material refers to BIOS as:

BIOS - The firmware flashed into the processor of a computer.

That just seems... horribly inaccurate right? Does BIOS "live" on the processor? I thought it was something that resided on the motherboard and helped with initializing hardware (including, but not limited to, the CPU).

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    In what context did the material do this? Was this intended as a general definition of "BIOS"? If so, it would be wrong even if the BIOS was always flashed into the processor. (Just as defining a human as "An animal with a backbone" is wrong even though humans are animals and do have backbones.) If it was describing a particular system where this is the case (there have been some where the BIOS happened to be stored on the processor's flash) then it could be correct, though only for that particular unusual system. May 11 '18 at 16:36
  • Maybe it's not "the firmware of the processor", but I'd definitely say the BIOS is the firmware (of the whole motherboard) and it does get loaded into the processor. The flash memory where it is stored might or might not be counted as a part of the processor.
    – Bergi
    May 11 '18 at 16:41
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    That definition would include UEFI as a BIOS, while both BIOS and UEFI are firmwares, but UEFI is a new kind of firmware interface for booting etc. BIOS is the old IBM-way of doing things.
    – Bakuriu
    May 11 '18 at 17:45
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    Yes, so the real answer is, no that is not the definition. It can be implemented like that, but not necessarily.
    – Mr Lister
    May 12 '18 at 7:48

What I am going to write perhaps surprises you: You seem to have assumed "processor" here to mean the central processing unit (CPU). This assumption originates from the IBM PC architecture seen in daily home computers. However, you are studying for CCSP, which means we are dealing with Cisco and its system-on-a-chip (SoC) architecture in this context.

While a BIOS is never flashed to a CPU, in a SoC, it is flashed to a processor chip. To quote from English Wikipedia:

A typical SoC consists of:

  • a microcontroller, microprocessor or digital signal processor (DSP) core
    • Multiprocessor SoCs have more than one processor core.
  • memory blocks including a selection of ROM, RAM, EEPROM and flash memory
  • ...

So, there really is a BIOS in this chip: Am286ZX/LX (SoC) Image: an AMD Am286 ZX/LX, a CMOS variant of the SoC version of the Intel 80286 CPU, made in 1991. (Image by Konstantin Lanzet, released under CC-BY-SA 3.0. Click to see the source.)

Nevertheless, if it were me, I wouldn't have written it like that. The prevalence of the IBM PC legacy means the writer must not neglect the mindset that is behind it.

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    Does Cisco actually refer to their firmware as a BIOS? I've never seen that before. Last I knew, the term BIOS refers specifically to the legacy BIOS firmware of IBM PC compatible computers (and incorrectly to the newer UEFI firmware and the configuration utility for both).
    – Wes Sayeed
    May 12 '18 at 0:13
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    I dunno where wikipedia gets there information of but my experience of looking at embedded designs powerful enough to run an OS is that the firmware is typically stored in a seperate chip, not in the "SOC"
    – plugwash
    May 12 '18 at 8:07
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    Actually the image is a bad example, since it needs an external (EP)ROM for a BIOS to function (see Page 13 of the Datasheet ) and does not have a ROM May 14 '18 at 9:21
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    @EUserNameError, I meant page 13 of the PDF linked, which describes the ROM I/F LCSROM. But look at page 22: ROM/EPROM [...] are attached as X-bus device [...] Then there are other peripherals mentioned you can attach. Also look at page 23 of the PDF and you see the default configurations with external ROMs. LCSROM is pin 191 on the chip... so you can attach a ROM...Am I interpreting this wrong ? May 14 '18 at 11:00
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    @EUserNameError, with some googl-fu I also found an article from 1991, regarding the release of this SoC - Quote "The manufacturer of a laptop or notebook controller needs only to add some RAM, EPROMs for the ROM BIOS, keyboard controller, a mass storage device, and a display to have a complete functioning system." May 14 '18 at 11:20

The code on the processor is known as the microcode. A form of firmware which resides on the processor and can be updated there from a running system

The BIOS exists on the motherboard, interacts with all the hardware to boot the machine to a point at which a bootloader can take over.

That said, if the material states this then this is the answer you should give on the exam.

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    +1 for "That said, if the material states this then this is the answer you should give on the exam." do this but also raise the correct statement as an argument when you get the chance. May 11 '18 at 14:55
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    @MustafaAKTAŞ yeah, sadly the people marking the exam may not know that the information on it is incorrect. Similar situation lead to me getting a job after pointing out half of the questions were too ambigious to be answered clearly. May 11 '18 at 16:23

The BIOS is firmware. It is located externally to the CPU.

The CPU is designed to read a fixed memory address when it receives electric power. The BIOS is located in that address, so the CPU executes the instructions located in it.

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    And most modern PCs use UEFI, not BIOS, so they usually don't even have a BIOS. (And if they do have one, it is emulated within UEFI and thus doesn't have live at a fixed memory address, or even in memory at all: it could be in a file on the filesystem, and loaded dynamically by UEFI.) May 11 '18 at 23:39

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