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An update on progress and some questions

Discussion in 'A+' started by Dream_In_Infrared, Oct 9, 2005.

  1. Dream_In_Infrared

    Dream_In_Infrared Nibble Poster

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    Hi all,

    Have been away from here for a few weeks, studying hard for the A+. It has been a fun time. Thanks for the recommendation of the Mike Meyer's "All in One" book. I am making much better progress using this compared to my last attempt at A+ with the Dave Groth book. MM's writing is clearer and easier to understand, quite funny in places, and his style makes it much more memorable. I have made it a third of the way through the book and slowly but surely chugging my way through.

    Have also completed a 3 week 'PC Building and Upgrading' at night-school course and start another 3 week course next week concerning 'PC fault finding and troubleshooting'. Between them they cover parts of the A+ and this has given me lots of opportunities to quiz the teacher about concepts in the MM book. We have done disk formatting, partitioning, OS installation and a PC build of a Pentium II system. I also took my own Pentium 4 system apart. [not earth-shattering news I know but it is all new to me] Am amazed, and mightly relieved, I did not lobotomise it in the process. The hands-on really helps but I know I need more and at the end of this month I intend to ask around local businesses for some work experience.

    I do have a couple of questions though. Firstly, is ROM BIOS loaded into RAM so that when the CPU needs to access the commands with which it talks to 'basic devices' [as MM calls them], it actually accesses the ROM BIOS commands residing in RAM and not on the ROM BIOS chip?

    Secondly, when the CPU wants a specific device to execute a specific task it uses I/O addressing. Forgive me if I muddle this. Assume, for example, that a hard drive is being accessed to save data within itself. The drive is referred to by a specific 'code' and the task it is being asked to perform is also know by a specific 'code', the two combining together to form the whole I/O address. This is the code the CPU needs to access from ROM BIOS in order for it to know that the hard drive wants to save data. The CPU accesses this code from ROM BIOS, puts it on the I/O part of the address bus and the hard drive saves because it has been given the commnd to do so. But how does the CPU know that it needs to access this specific command, pertaining to this device and this task, in the first place? I assume it something to do with the device sending an IRQ and possibly using the address bus to communicate a specific instruction to the CPU.

    Argh. :bigcry: Sorry. Am kinda befuddled on this point. Have understanding of various bits but the key is making the links between them. :o

    Thanks for any clarification that may be forthcoming.
     
    Certifications: None :(
    WIP: A+
  2. Dream_In_Infrared

    Dream_In_Infrared Nibble Poster

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    OK, I think I have the answer to question 1. A link Jakamoko posted on another thread about RAM mentions Shadow RAM as being the place where BIOS commands are stored. :biggrin

    However, can someone please help me with question 2?
     
    Certifications: None :(
    WIP: A+
  3. Jakamoko
    Honorary Member

    Jakamoko On the move again ...

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    Sorry you didn't get a response before now, D_I_I - hopefully your 2nd question will get an answer soon (unfortunately, I'm elbow-deep in the machine that caused me to unwittingly answer your first question :rolleyes: )
     
    Certifications: MCP, A+, Network+
    WIP: Clarity
  4. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    Why does it matter? ROM and RAM are mapped to an address - either will work. Quite often ROM will be copied to RAM, but this is only because ROM can be quite slow.

    Note that either version of BIOS will not be used once the OS is booted - the services offered will be too limited, and the OS drivers will do it better.

    Not quite. The drive 'code' and the action 'code' are passed to the BIOS or the driver for that particular system, along with a pointer to any extra data. The IO address is burried in the BIOS or driver.

    If, on the other hand, you are looking at the action of the BIOS/driver rather than the OS, then the two codes are normaly placed in various IO addresses for that device for the action to take place.


    It will have determined (in the OS) which device it needs to talk to, so will have the appropriate info


    Hope this helps,

    Harry
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+
  5. Dream_In_Infrared

    Dream_In_Infrared Nibble Poster

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    Thanks for clarifying both points. Makes sense now. :biggrin

    I understand that device drivers are more important than ROM BIOS nowadays but I still wanted to understand the idea. I would prefer to know what is going on rather than just accept what I am told. I am an inquisitive soul and need to know. ;)
     
    Certifications: None :(
    WIP: A+
  6. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    Sounds good to me! That's the way I work as well!

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+

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