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Author Topic: How do Intergrated Circuits work?  (Read 3542 times)
PlyPencil
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« on: November 01, 2008, 04:42:26 AM »

Okay, I am talking about processors, such as for Computers. They contain millions if not billions of transistors which can either have a value of 1 or 0 to process data. What I want to know is how energy going in, changes the transistors value to either open (0) or closed (1) and leaves.

That is all I would like to know
Thanks
Ply.
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Tiak
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« Reply #1 on: November 01, 2008, 06:40:23 PM »

Okay, I am talking about processors, such as for Computers. They contain millions if not billions of transistors which can either have a value of 1 or 0 to process data. What I want to know is how energy going in, changes the transistors value to either open (0) or closed (1) and leaves.

That is all I would like to know
Thanks
Ply.
Well, to start off, you seem a little mistaken about what a transistor is.  A transistor is essentially a sort of switch that has three inputs, and one output.  Basically, there is an input voltage, and an input that, when applied allows voltage to flow from this input to the output.  In theory, just about any device that can be used to switch current flow on and off could form a computer.  It would be possible to build a computer that operates entirely based upon robotic arms and light switches (though this would be mindblowingly slow).  Likewise, vacuum tubes, and relays, other types of switches have been used in the past to form computers before we had the technology to form transistors reliably.

It is networks of these transistors that allow data to be processed, these networks, when given a certain combination of input, will flip certain switches such that there is a certain output based upon that input.  The next level of abstraction up, based upon these transistors, is a logic gate.  A logic gate is a circuit that takes two inputs and has one output depending upon what those inputs are.  There is a sort of logic gate for every combination of outputs and inputs, and these can be used to do things like add single binary digits.

Let's say, for example, we have two inputs, and we want to add them.  Well, we know to carry the result over to the next highest digit if, and only if, both these inputs are on.  So we use an AND gate, which will output 1 if it receives 2 1's as input.  Likewise, for the result of the digit itself, we want to output 1 if one of the two inputs is a 1, but not both.  For this, we would use an exclusive or gate. 

Wider networks of these logic gates allow computers to do the various computations they do, as well as temporarily store some data to operate on.
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Thek3mp
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« Reply #2 on: November 01, 2008, 08:00:40 PM »

a wow thats complicated, il stick to rigging school stairways with smoke bombs.
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Seb
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« Reply #3 on: November 01, 2008, 08:28:38 PM »

a wow thats complicated, il stick to rigging school stairways with smoke bombs.
Why not grenades/live shells/ bombs?
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Araeus
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« Reply #4 on: November 02, 2008, 04:39:18 AM »

You think that's complicated, try building a processor out of (essentially) basic logic gates.  I absolutely hated that project...

We were using a program, not actually building them, but the idea is the same.  You built all the individual pieces for the processor over the semester and then in the end you took them and set up a (hopefully) working processor.  Granted this processor could only really do simple math (add, subtract, multiply, divide, bit shift, and, or) and save or load values from it's own RAM... but still... I was pretty blown away when we were done...
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PlyPencil
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« Reply #5 on: November 02, 2008, 06:59:33 AM »

Wow thanks, thats made it a lot clearer in my mind 1, what program did you use to build your model?
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Adramalech
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« Reply #6 on: November 02, 2008, 07:17:48 AM »

you can also play 'garry's mod' with 'wiremod', then you can build your own contraptions and control them using wiremod, which lets you place things like logic gates (and all sort of other processory thingys).
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Araeus
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« Reply #7 on: November 02, 2008, 06:53:53 PM »

We programmed it in Verilog, which I wasn't a big fan of although I'll have to admit it's the only one I've seen that lets you build something like that easily.
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setech
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« Reply #8 on: February 20, 2009, 08:42:18 AM »

Tiak got it quite right (except that on a transistor there are 2 inputs and 1 output, not 3 inputs, but seems like a semantic typo)..

Your best bet on understanding this kind of stuff is playing with it.

Anyway, if you are interested in the low level workings of your computer, then you should start at Boolean logic (and, or, not, xor, nand, etc). Especially the NAND logic is interesting for IC's, because it can express everything. That's why most circuits are built of only a bunch (e.g. millions) of NAND gates. This is not that hard, but some folks still don't get it.

Then you go to the basic functionality of transistors and logic gates (which Tiak explained really well). In your endevour about transistors you will also encounter (MOS)FETs (field effect transistors) and CMOS, which are magnified/extended transistors and are used the most in IC's.

After you are done with the basics, you can play around with Programmable logic controllers. These are best fit for implementing simple logic circuits that control stuff (they are used for most of the industrial automation equipment that is below robotics level, e.g. CNC axes and production lines). These are your best bet to get something hands on for a few hundred bucks on a model level.

Programming with Verilog seems to be interesting (never did that one, I like the hands on approach much better), but to design an integrated circuit only makes sense if you have access to FPGAs (field programmable gate arrays) or ASIC's production (hey, it's not really fun to design something that never gets implemented :p) Of course in a technical university you probably still have to do this, because they never let you play with the good stuff, and want to tourcher you with theoretical stuff until you lose your will to live on.
« Last Edit: February 20, 2009, 10:27:08 AM by setech » Logged

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