View Full Version : BIOS and CPU Interaction?
Hey Every1,
Studying for my A+ exam under Mike Meyers guidance, he has said in his book that the CPU for example, talks to the BIOS program to extract what exact letter was pressed on the keyboard.
I tend to get confused on this point because I belive that the CPU is just a piece of hardware in the computer that executes software instructions.
So am I right to say that the operating system asks the BIOS for what key was pressed in this situation and not the CPU??
I believe that it is the OS that talks to all BIOS programs which in turn the BIOS programs talk to the hardware.
Does sound right to you at all??
Cheers friends
Beno
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Have a nice day
YODA74
10-29-2001, 06:59 PM
Beno Good topic take a look at this it'll give a short run down of process.It Won't explain the exact task of the CPU but gives a start.
http://www.pcguide.com/ubb/Forum1/HTML/000259.html
A CPU is similar to a calculator, only much more powerful. The main function of the CPU is to perform arithmetic and logical operations on data taken from memory or on information entered through some device, such as a keyboard, scanner, or joystick. The CPU is controlled by a list of software instructions, called a computer program. Software instructions entering the CPU originate in some form of memory storage device such as a hard disk, floppy disk, CD-ROM, or magnetic tape. These instructions then pass into the computer's main random access memory ( RAM), where each instruction is given a unique address, or memory location. The CPU can access specific pieces of data in RAM by specifying the address of the data that it wants.
As a program is executed, data flow from RAM through an interface unit of wires called the bus, which connects the CPU to RAM. The data are then decoded by a processing unit called the instruction decoder that interprets and implements software instructions. From the instruction decoder the data pass to the arithmetic/logic unit (ALU), which performs calculations and comparisons. Data may be stored by the ALU in temporary memory locations called registers where it may be retrieved quickly. The ALU performs specific operations such as addition, multiplication, and conditional tests on the data in its registers, sending the resulting data back to RAM or storing it in another register for further use. During this process, a unit called the program counter keeps track of each successive instruction to make sure that the program instructions are followed by the CPU in the correct order.
Wiffy says time to chow down. Later
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[This message has been edited by YODA74 (edited 10-29-2001).]
geebee76
10-31-2001, 07:47 AM
Hi Beno, good question!
Post back if you figure this one out, I'd be very interested in your conclusions.
In the meantime I will continue to try to figure this out myself.
I suspect the answer to this will be quite complex with many variables.
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Hey GeeBee,
Yeah I still can't come to it, but I think you can think of it as the Op.Sys which scans for BIOS interaction for which the CPU carries out.
Can't wait to get the answer to this.
I don't have time at the moment but you can email Mike Meyers at totalseminars
I think its mikem@totalsem.com or mikem@totalseminars.com
This guy was the guy that wrote the book and is a really helpful friendly guy.
Cya mate
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Have a nice day
bassman
11-01-2001, 09:22 AM
OK gentelmen,
Lets imagine for a moment that there actualy is something intelegent and thinking inside that white box. That would be the CPU. It is what asks for info, takes in info, thinks, and produces a solution. The OS is a big stack of books that tells the CPU how to communicate and interprete info from other devices and software. Remember, the OS is only the part that has the instruction sets. Not all the other fluff the is included with the install (media player, solitaire, defrag,...)
SO, if a call comes in from the keyboard BIOS, it is the CPU that is receiving this call. It may need to refer to some instructions in the OS to be able to understand, but it is still the CPU getting the call.
Does that help? http://www.PCGuide.com/ubb/wink.gif
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geebee76
11-01-2001, 10:21 AM
Bassman, keep it coming http://www.PCGuide.com/ubb/tongue.gif
How does this sound?
Imagine you have Wordpad or similar open on your desktop.
You then press the letter "A". The keyboard controller deciphers, which key was pressed and stores this information. It then interupts the CPU, saying "a key has just been pressed on the keyboard". The CPU can't talk to the keyboard controller because it doesn't know what type of controller it is. Instead it talks to the BIOS, saying "I need to use one of the little keyboard programs you store, to access the controller and extract the information stored there". This little program tells the controller to put the code onto the data bus for the CPU to read.
Ok so far? http://www.PCGuide.com/ubb/eek.gif
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bassman
11-02-2001, 12:36 AM
OOOOOO, I like that hehehehe http://www.PCGuide.com/ubb/biggrin.gif
I always enjoy Demystifying these machines by pretending they are a little bit human in order to analogize the true machanical aspect of them http://www.PCGuide.com/ubb/wink.gif
Boy, if I had to say that out loud, my tongue would be sore http://www.PCGuide.com/ubb/biggrin.gif http://www.PCGuide.com/ubb/tongue.gif
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Paleo Pete
11-02-2001, 10:42 PM
OK, I got the "press the letter A" part... http://www.PCGuide.com/ubb/biggrin.gif
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Hey Guys,
Continuing on from GeeBee, once the CPU knows what letter was pressed on the keyboard...........it goes hmmm..the letter 'A' was pressed.
Well what I will do know is give that letter to the Op.Sys.
The Op.Sys goes cool......the letter 'A'......well I will give that letter to the appication that is currently open and from there, it will be displayed onto the screen.
Does this sound right Paleo Pete or any other guru's out there?!
Cheers
Beno
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Have a nice day
Oh yeah,
just continuing on from that last message of mine.
When the CPU gives the letter back to the Op.Sys.......I assume it does so again through the BIOS..........can someone correct me here if I am wrong please.
Beno
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Have a nice day
geebee76
11-07-2001, 12:22 PM
Hi Beno, I'm still with you on this http://www.PCGuide.com/ubb/eek.gif
The trouble is that I keep coming across conflicting information.
I think the point you are making about the role of the OS is a
valid one, which I'm looking into right now.
I think the trouble is that when people like Mr Meyers write about
complex subjects, they have to leave some of the processes out otherwise
they would end up with a 5000 page book costing $300, which us learners
wouldn't understand.
Unfortunately because of these constraints we are sometimes left asking
questions and attempting to draw our own conclusions.
If there is anyone else out there that has knowledge about this subject
please feel free to jump in with your comments. Also if anyone knows
of an Internet source or a good book, I'd appreciate a pointer.
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You are making progress if each mistake is a new one!
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Hey GeeBee,
Mate I think your absolutely right there about making assumptions about complex processes. You have to have a very imaginative mind when trying to visualize things like this ehh!
But make sure you keep me up to date on this topic by posting to this link.
I think by knowing this info will stand us in a better technical understanding than a lot of other people.
I will keep trying to search for a complete and thorough answer to this one as well
Cheers
Beno
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Have a nice day
I think one very important point here is being over looked.
Unlike many people the CPU can in fact “Walk and Chew Gum at the same time”
While the CPU is talking to the Keyboard Program it is also talking to the Memory controller
That is Holding hands with the OP.sys that is talking to the program stored in Ram.
By way of the CPU.
All the while waiting for the A to be added to the Word processor program
To start the Sentence A Quick Brown Fox
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Hi Rick,
That is not a very clear answer that I can go across.......I mean you can obviously tell that me and GeeBee are a bit lost on this subject so we need as much detailed explanation as we can.....maybe a website URL to point us in the right direction would help.
Maybe you could do that for us.
Thanks mate
Beno
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Have a nice day
Beno
A good start point is here for the CPU http://www.extremetech.com/article/0,3396,s%253D1005%2526a%253D1621,00.asp
And Here for the Mother board
http://www.extremetech.com/article/0,3396,apn%253D2%2526s%253D1005%2526a%253D1059%252 6ap%253D1,00.asp
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To ERR is HUMAN
To REALLY screw things UP, YOU NEED a COMPUTER !
When I press the A the keyboard controller .
Sends an interrupt ( IRQ Level 1) to the CPU.
Asking/Telling it to pause and listen
This is done without the need for an Operating system.
It is controlled by the Bios.
Bios Being ..Basic Input Output System
http://www6.tomshardware.com/mainboard/97q1/970101/
What the CPU does with that A is controlled by what Instructions the CPU following at that time.
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To ERR is HUMAN
To REALLY screw things UP, YOU NEED a COMPUTER !
chall67
11-17-2001, 10:38 PM
Your keyboard is assigned an IRQ number, as you may well know, IRQ stands for Interrupt Request Number. Whenever you punch a key on the keyboard, that device sends it's IRQ signal down the BUS line to the CPU to let it know that it needs attention. The CPU then stops whatever it was doing when it got this request and processes the request by retrieving an address that is stored in memory and sending a signal back to the requesting device acknowledging it's request therefore completing the process of your keystroke.
Man..I sures hell hope I explained that decent enough, anyway good luck with your A+ studies, I'm also studying for my A+ certifacation and can use all the help I can get. As you can see, I can't even spell certifacation.
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Thanks Chall67,
that helped reinforce my understanding
Cheers Mate
Beno
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Have a nice day
ranchdog
11-18-2001, 08:48 AM
Wait. Wait. Wait.....
I haven't grasp the "press the letter A" part yet.
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[This message has been edited by ranchdog (edited 11-18-2001).]
YODA74
11-18-2001, 09:22 AM
Rick I think one very important point here is being over looked.
Unlike many people the CPU can in fact “Walk and Chew Gum at the same time”
While the CPU is talking to the Keyboard Program it is also talking to the Memory controller
That is Holding hands with the OP.sys that is talking to the program stored in Ram.
By way of the CPU.
All the while waiting for the A to be added to the Word processor program
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I kinda grasp what your saying here maybe I'm misunder standing,but without the chip set the cpu can't walk and chew bubble gum at the same time, http://www.PCGuide.com/ubb/biggrin.gif isn't the chip-set like the the middle man in all this or ahh the traffic cop with out it nothing goes anywhere?? or is that what your saying by memeory controler? I'm a little illiterat here on inter workings
just trying to grasp this here. http://www.PCGuide.com/ubb/biggrin.gif
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[This message has been edited by YODA74 (edited 11-18-2001).]
Yoda
The Chipset /Bios is the middle man between the components on the system .
Basic In/Out system.
With out it the components wouldn’t know how to talk to each other or Even where to send the message.
Interaction between them is impossible without it.
Assigning an IRQ to each or in the case of the PCI bus sharing the Irq’s
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To ERR is HUMAN
To REALLY screw things UP, YOU NEED a COMPUTER !
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