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What exactly are the bare minimums you need for a computer to boot? Like lets say. I want to make a small computer that just runs a constant security check. ...
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  1. #1
    Just Joined! dethklok02895's Avatar
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    Bare Minimum


    What exactly are the bare minimums you need for a computer to boot?

    Like lets say. I want to make a small computer that just runs a constant security check. Lets say for a security system I installed for my house. I dont need to keep log files or anything just need to run a constant check (or only when the security pad is accessed).

    Just interested on what you need not what you should have without a POST error.

  2. #2
    Linux Guru Jonathan183's Avatar
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    For that sort of system you would be better off using something like a microcontroller example PIC - which you could get with built in program and temporary storage memory.

    Ed: it's about 14 years since I setup and used a PIC processor ... I used PIC as an example of a microcontroller - which I think is better suited to the sort of application you mentioned than a general purpose computer with separate processor/RAM etc. It is also likely to be more robust than a system with separate RAM etc.

    Something opensource based is the way to go if you can

    POST is optional - the code which is executed from the processor start address is up to you - but in order to cut out POST you need to write to that area of memory (which is more involved, possible, but can also result in a system which does nothing )
    Last edited by Jonathan183; 03-24-2012 at 01:42 PM.

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    or a raspberry pi

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    Speaking of the Raspberry Pi, it will run a version of Ubuntu, as I remember. You can download the image for it and see what a really tiny computer needs to boot. That should answer your questions.

    Other than a kernel, you have to deal with each and every hardware device on a system. That includes the motherboard bridges, drives, and I/O. That's what make designing an embedded system a little tough.

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    Use the Arduino!!!

    Quote Originally Posted by dethklok02895 View Post
    What exactly are the bare minimums you need for a computer to boot?

    Like lets say. I want to make a small computer that just runs a constant security check. Lets say for a security system I installed for my house. I dont need to keep log files or anything just need to run a constant check (or only when the security pad is accessed).

    Just interested on what you need not what you should have without a POST error.
    Theoretically, all you need for it to "boot" is a single program that does what the computer needs to do, and nothing else.

    A single function computer that sits around waiting for a signal simply needs to have a few instructions written in assembler and installed into the machine's firmware. Copy the instructions to memory address 0x0000 (or wherever the CPU is hard-wired to look first when it is powered on). As soon as power is applied and the clock is running, the CPU will read the first instruction at this address and execute it, and that first instruction is usually an instruction to load a cascade of other instructions, all of which the computer will execute one by one.

    On larger systems, this first set of instructions is usually a power-on self-test (POST) program that just checks for hardware attached to the motherboard. Then the POST program reads a boot-loader program from a hard-wired location. When the boot loader program runs, it locates the operating system kernel program from a disk or memory device, and then executes that kernel program.

    But that entire process is not necessary, that is just the standard process used in the industry to make servicing and setup easier. If you want, you could replace the POST with your own security alarm program.

    Check out the Arduino, it is a simple microcontroller that is 100% open source. The software to program it is all available in Linux. You can write the assmbler and compile it to a binary program, then copy the binary to the device via USB. Just connect it to your computer via USB, and it acts like a standard teletype terminal, which you can access via the file "/dev/ttyUSB0".

    The Arduino is well documented, easy to learn, and has thriving online community of helpful fellows to assist you if you get stuck with something.
    elija likes this.

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    Just Joined! dethklok02895's Avatar
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    Alright Cool ideas. When I get my stuff in the mail. I'll do some Frankensteining and see what I can come up with.

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    Penguin of trust elija's Avatar
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    You should blog it as it sounds like you are going to have fun
    "I used to be with it, then they changed what it was.
    Now what was it isn't it, and what is it is weird and scary to me.
    It'll happen to you too."

    Grandpa Simpson



    The Fifth Continent

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    Just Joined! dethklok02895's Avatar
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    Most likely not elija I'm getting 5 broken laptops. And supposedly another box full of random parts (i.e. resistors, Circut boards, capacitors, speakers, etc.).

    I might only accomplish electrocution or a fire.

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    Linux Guru Rubberman's Avatar
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    Quote Originally Posted by dethklok02895 View Post
    Most likely not elija I'm getting 5 broken laptops. And supposedly another box full of random parts (i.e. resistors, Circut boards, capacitors, speakers, etc.).

    I might only accomplish electrocution or a fire.
    Yes, there are a lot of opportunities here to let the smoke out! I should sic you on my grandson. He's in hog heaven when someone gives him a box of broken computers and electronics parts. Before you know it, he'll have built an entire cadre of AGVs (Autonomously Guided Vehicles)!
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  11. #10
    Penguin of trust elija's Avatar
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    Quote Originally Posted by dethklok02895 View Post
    Most likely not elija I'm getting 5 broken laptops. And supposedly another box full of random parts (i.e. resistors, Circut boards, capacitors, speakers, etc.).

    I might only accomplish electrocution or a fire.
    So now I'm thinking you tube
    "I used to be with it, then they changed what it was.
    Now what was it isn't it, and what is it is weird and scary to me.
    It'll happen to you too."

    Grandpa Simpson



    The Fifth Continent

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