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To: TimF who wrote (64218)	11/21/2001 2:52:44 PM
From: Pravin Kamdar	Respond to of 275872

Tim, You don't have to be Newton to understand what you are missing. There is some tiny little light bulb that needs to go off in your mind to clear this up (I was at pain to say, "that needs to switch on"). You need to look a diagram of two cascaded inverters to see what is going on. Have fun with it. Pravin.

To: TimF who wrote (64218)	11/21/2001 3:11:10 PM
From: milo_morai	Respond to of 275872

Tim here's a start et.nmsu.edu Here's a program you may like hallogram.com stumbled on this page but it's very basic dccworkstation.com

To: TimF who wrote (64218)	11/21/2001 3:25:14 PM
From: combjelly	Read Replies (1) \| Respond to of 275872

"But how does that switch change from open to closed?" Tim, the only physical switch that is needed is the one on the power supply. Once a voltage is delivered to the system, it gets initialized to a known state and proceeds from there. Computers are almost like fractals, you keep finding the same structures and functions as you zoom in. In this case, we start with basic transistors. Before anyone else jumps in, this is really simplified, I am assuming the transistors are used linearly and am ignoring the resistors and other components that would be used in a real circuit. Voltage (and current), flows from the emitter to the drain. The gate controls that voltage. Depending on the transistor type, it either works as an inverter, i.e. the voltage on the drain is opposite that of the gate, or a buffer, the voltage at the drain matches the voltage at the gate, only it has more current (usually). Now just inverters or buffers aren't all that useful, you need to have multiple inputs to make them really interesting. So the transistors are combined to form AND, OR and exclusive OR gates (XOR). An AND gate requires all the inputs to be high for the output to be high, an OR gate needs one or more inputs to be high, and an XOR needs one or the other input to be high, but not both. And then these gates are combined to form more complex structures like flip-flops, counters, adders, multiplexers, etc.

To: TimF who wrote (64218)	11/21/2001 4:39:38 PM
From: TGPTNDR	Read Replies (1) \| Respond to of 275872

Tim, Your problem seems to me that you can't picture the 'first' switch. I visualize that first switch as existing in the software of the program interacting with the software of the operating system. The program says 'take the data at this logical location'. The OS says 'that logical location is this physical location -- CPU, send a request for that data' and the cpu closes the switch to get the data. My visualization only. tgptndr

To: TimF who wrote (64218)	11/22/2001 2:45:06 PM
From: RayMarv	Read Replies (1) \| Respond to of 275872

"But how does that switch change from open to closed?" It sounds to me that maybe you are looking for the ‘prime mover’ in all of this which is the program. The program counter is a register that is initialized at reset to point to a specific memory address in the PROM that contains the BIOS which is the first series of instructions to be executed. Each instruction consists of the 1s and 0s that start the avalanche of switching to begin. At the end of the instruction the program counter is either incremented to the next instruction or changed to point to another memory location and begin on that instruction. Is this closer to what you mean? Marv