starting a computer without any Firmware/BIOS

February 3, 2010 at 02:00:02
Specs: Linux i686
Can any body please tell me the behavior of computer hardware in such a case when there is no Software (OS) or firmware (BIOS) etc in it.

I want to know the power behavior in such a case. i.e. when we give power to the computer then what would it affect on the hardware components. I mean what do they do?

Before the power they were sorf of dead and after getting power whether they start to expect something or do the go on to some known state?

what is the Phenominal change after the power up.

Can i get any information regarding this ??

(I have mentioned that there should be no software as we all know that on power, the software usually drives the hardware but what happens when there is no software)

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February 3, 2010 at 02:18:59
Without a BIOS and software nothing happens, sod all, not a thing.

Without a BIOS or software all you have is a collection of electronic bits and pieces that does nothing.


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February 3, 2010 at 06:48:58
As StuartS says nothing happens at LOGIC level as there is no programmed directives to activate any process, the function BIOS and software are aimed to do.

At PHYSICAL level after power on the electronic circuits are biased but nothing further.

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February 3, 2010 at 09:27:09
A hardware question. Not a programming question.

Helping others achieve escape felicity


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Related Solutions

February 3, 2010 at 21:34:58
@ StuartS and IVO

Actually I want to know from a naive point of view.

As we all know that BIOS is the thing that is started when we power on the computer and it then gives instructions to all the devices to do some particular thing.

But in the same way when the power is given to a particular hardware device say RAM then it may perform some self test or something to be ready for instructions from BIOS.


After power on:

- The RAM may initiate some of its registers.
- May increment any counter.
- May get itself ready for input.

and other hardware components may do this as well ...
I want to get this information. The phenomenal change !!

@ Mechanix2Go

You are right that its not particularly programming related question and i asked it in hardware section but the moderator has put it here :)

But I think it may has some link with the programming.

I want to know the behavior of hardware without any software so that I could understand the impact of software instructions on the hardware when we give them power.

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February 3, 2010 at 22:36:49
well, i think it's a fair and relevant challenge. I am curious about these things also (boot-up sequence). I'm sure there's a lot "out there", but nine tenths of solving a question is asking it the right way. (google rocks, btw,). I think it would be awesome to be able to interact with the machine during bootup (kind of a super-debug running off another machine) and i'm sure it's been done (maybe burn a custom bios chip, but no.. i'm behind times here, grasping!) My experience is that if RAM is any way compromised vs what the bios needs, or expects, to run, the whole show is over.
Bios sends "packets" over the bus to enumerate/initialize/validate/analyze devices and loads or requests loading of their respective bios contents (plug+play)
There's cache ram and main ram.
there's the end of my knowledge and sorry for using up forum bandwitdth.

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February 4, 2010 at 02:22:35

Well thats what i m thinking for :)
and I can not be able to get the relevant information regarding this issue. All the stuff in the internet t just tells the boot process when there is BIOS present.

But if there is no BIOS then they say that the system will not do anything... Well I don't agree with this.

the hardware still does something .. It goes in to some particular state. I want to know what is that ... simple (or is it ?? :D)

Can anyone know about the instructions the BIOS uses to communicate with the hardware components.

How BIOS identifies the identity of a particular device ?

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February 4, 2010 at 03:00:15
planetcode_2, I don't understand what you are looking for as you qnswered by yourself to your question.

I admit I was interested by your question and guessed it was posted by a novice to computer systems, but the example you reported about RAM initialization reveals you have a good knowledge of digital architecture.

Anyway when you power on the system you just modify its electrical status, i.e the integrated circuits are biased, potential gradients are established and P/N junctions activated inside semiconductors. What follows may be due to firmware or wired logic. That depends on the architecture of the components or the whole system.

The process you reported about RAM may be activated by its own firmware (internal RAM BIOS) or a wired initialization logic. The border between pure hardware and firmware is absolutely tiny (see the long debate CISC vs RISC architecture for CPU).

While the computer as we know was theorized by von Neumann that assigned a focus role to the Program stored in RAM, there are studies for general purpose computers based on harqware only, i.e. softwareless (Symbol was such an exparimental machine in 80s).

So the role of firmware/software is not absolute but is assigned by the whole design planned for the system.

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February 4, 2010 at 04:10:00
But if there is no BIOS then they say that the system will not do anything... Well I don't agree with this.

When a PC starts up and power is supplied to the CPU it goes through its own initialisation. At the end of this initialization it puts address 0000FFFFH onto the address bus and starts executing code at that address.

The address 0000FFFF is always in the BIOS. It has been like that ever since the IBM PC was made in 1982. It is at the top of end of the original 1Mb of memory that the first IBM PC could address.

These days the first instruction at 0000FFFF is usually a Jump instruction which takes it to another place in the BIOS and continues execution from there starting of with the Power On Self Test. It doesn't matter how much software is on the hard disk or how much software might be stored in memory, if the BIOS isn't there there is no way the CPU can get at it.

If the CPU cannot find any executable code at this address then it just stops, goes into a wait state and does nothing. If the CPU is not executing instructions, then nothing happens. The only way to get the CPU out of this wait state is to press the reset button and it does it all over again until such time as it can find some code to execute.

If you want to understand more about what happens you need to delve into just how the CPU does its stuff. How it interacts with other hardware, particularly memory and how the various registers within the CPU control exactly what the CPU does.


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