Computer Architecture : is 0 really 0 ?
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I know that, but it doesn't answer the question.
You'll never get very far if all you do is follow instructions.
right quick explanation if you read Andrew Torrence explation http://www.codeproject.com/Messages/4868169/Re-Computer-Architecture-is-really.aspx[^] that gives some of it. The rest you can get from howstuffworks.com or as Andrew says don't worry too much about the details.
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CPallini wrote:
voltages, not currents
Yes, but can you have one without the other?
You'll never get very far if all you do is follow instructions.
The closest that you could get is a battery hooked up to a capacitor. A capacitor is just a gap in the circuit with a large surface area. Electrons pile up on one side and the force they exert on the other side repels the electrons on that side. Of course there is always leakage current in real life, and things get a little more complicated with A/C. http://en.wikipedia.org/wiki/Capacitor[^]
Curvature of the Mind now with 3D
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I thought it was just a complex superposition of 2 states, which ends up giving you 3 dimensions to work in so you can get things like 30 degrees away from true. :-D
Curvature of the Mind now with 3D
Well, I'm still fuzzy on all of it, but from what I gather that's what it's intended to represent. But it still has to be stored somehow, the third state is a "indeterminate" flag to say it could be anything. But, it's still three states stored in the system.
Jeremy Falcon
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-5v? I can't see how you can have tristate binary. What sort of logic was this?
Regards, Rob Philpott.
Rob Philpott wrote:
-5v? I can't see how you can have tristate binary. What sort of logic was this?
Its a matter of interpretation. The physical characteristics are represented by a tristate value while the actual usage relies on two state values. A more esoteric example is in RS 232 protocols where 1 and 0 are represented by how the slope of the electrical signal is moving. You can google for the following to see pictorial representations of that. rs232 falling edge That said there is a idiom (or 'theory' maybe about 3 state logic) which is discussed in the following http://en.wikipedia.org/wiki/Three-valued_logic[^]
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Vivic wrote:
tit is a kind of bird
Nah, it's what birds have two of.
You'll never get very far if all you do is follow instructions.
That is true too. You just phrased it very well. I didn't figure out how to use 'bird' meaning 'girl'!
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in computers' circuits is the bit 0 really represented by no currency or it is a small signal that the computer is made to treat as 0 ? thank a lot !
In a -5 to 5 volt system, minus values are treated the same as positive. the 0 is in between 0 and 0.8 and the 1 is in between 2.5 volts and 5. Panasonic developed three state chips which read 0.8 to 2.5 volts as a third value.
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There is a problem with ternary logic. "Bit" is short for "binary digit". What would you shorten "ternary digit" to? The problem is equally terminological as technical! PS. In the UK, I am aware that a tit is a kind of bird.
Vivic wrote:
"Bit" is short for "binary digit".
What would you shorten "ternary digit" to?"tet" of course! ;P
GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
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in computers' circuits is the bit 0 really represented by no currency or it is a small signal that the computer is made to treat as 0 ? thank a lot !
I always thought zero was 1070/2025 Hz and 1 was 1270/2225 Hz (that is up/down). At least that is how 0 and 1 was represented when I learned my first BASIC programming. Oh well, that was way back in late 1975. Maybe newer implementations use different representations.
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Certainly, at a software level. But I've yet to see any sort of bus that uses three logic levels.
Regards, Rob Philpott.
in many case three state of currency doesn't mean three state of logic. The -5 / 0 / +5 differentiation is used just for electrical reason. If use 0 / +5 you can have a sort of eco in the signal wich transform it self into noise. With negative voltage there is a resorption of this eco but the chipset will not see the zero. Practically is -5 for false and +5 for true
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in computers' circuits is the bit 0 really represented by no currency or it is a small signal that the computer is made to treat as 0 ? thank a lot !
Every circuit has noise and dark current, both of which tend to increase with temperature. Whatever the circuit treats as a logic 0 or 1 is within a certain tolerance. Marc
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in computers' circuits is the bit 0 really represented by no currency or it is a small signal that the computer is made to treat as 0 ? thank a lot !
In a lot of chips I've worked with there is an internal threshold (sometimes external resistor) that if the voltage is above "X" it is on, if below it is off. Serial ports work like this with either a 5vdc reference or a 2.5vdc reference and then is split down the middle. there is an effect called field magnetism (bleed)where other external voltages can influence (and will) the wire voltage so you never get a clean 0vdc. So chip manufactures tend to build this into the chips. a signal could look like: 4.5, 1.2, 3.8, 0.6, (on,off,on,off) and still be perfectly valid, that's where oscilloscopes come in handy for troubleshooting. :)
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Rob Philpott wrote:
What sort of logic was this?
In computing - Three state logic. In formal logic there is also ternary logic, in one scheme: +1: True 0: Unknown/ Indeterminate -1: False You've probably already used this without realising, nullable bit fields in SQL work along ternary logic lines.
Alberto Brandolini:
The amount of energy necessary to refute bullshit is an order of magnitude bigger than to produce it.
Keith Barrow wrote:
In computing - Three state logic.
Yeah, it's technically possible, but indeterminate boolean values make my skin crawl. They aren't even boolean, really.
Keith Barrow wrote:
You've probably already used this without realising, nullable bit fields in SQL work along ternary logic lines.
And this is exactly why I hate them. You can have nullable bit fields, but you can also hit the server with a hammer, that doesn't make it a good idea. I'm sure there are some cases out there where this is useful, but I've only found it to be problematic. Every time I find nullable bit fields in a database, it's an issue that needs fixing rather than some clever use of three-state logic. If you need more than two values, why even use a bit field for that? Integers will do fine, and you won't have to deal with nulls.
Keith Barrow wrote:
In formal logic there is also ternary logic, in one scheme:
+1: True
0: Unknown/ Indeterminate
-1: FalseYeah, but in general classical logics don't allow indeterminate values. True, false, or GTFO.
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in computers' circuits is the bit 0 really represented by no currency or it is a small signal that the computer is made to treat as 0 ? thank a lot !
The reality is that all circuits are really analog, they don't instantly change from one state to another. So, the transition is never at one extreme or the other. If the chip claims to work at say 0 and +5 there is some point before +5 that the circuit decides the signal is a 1 and some point before 0 that it decides that the signal is a 0 (replace 0 and +5 with your favorite voltages for representing 1 and 0.) In diagrams they like to draw straight lines and sharp corners but the reality that none of the lines are straight and none of the corners or sharp. In fact, there is usually some amount of overshoot at the corners and a certain amount of settle time. They have a couple of pictures here of what overshoot looks like. So, if they used the 0 or the +5 for the actual 1 and 0 indicator it would get very tricky because the signal (at least at the corners) tends to bound around the min and the max voltage...
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Vivic wrote:
"Bit" is short for "binary digit".
What would you shorten "ternary digit" to?"tet" of course! ;P
GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
I find that offensive.
You'll never get very far if all you do is follow instructions.
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in computers' circuits is the bit 0 really represented by no currency or it is a small signal that the computer is made to treat as 0 ? thank a lot !
Not sure what you mean by currency. You generally have voltage, current, and resistance. As for 0 and 1, generally this is a measure of voltage only. And most of the time 0 is near ground potential and 1 is near Vcc (the voltage common to the circuit). So if your wondering if there might be some amount of residual voltage - yes. In fact it with a typical circuit, most of the time the pins will not be exactly or Vcc. They will be slightly higher than 0 or slightly lower then Vcc. And occasionally, you can actually et something that is very close to half way between, but such a situation is generally a result of some problem in the circuit. Having said all this, in most cases in working with a digital circuit it helps to set the scale and simply lance at the value. High and low will be very obvious.
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in computers' circuits is the bit 0 really represented by no currency or it is a small signal that the computer is made to treat as 0 ? thank a lot !
I saw a lot of good answers here, but wanted to point out that there are some very common devices in personal computer architecture that use multiple voltage levels to represent more data - MLC solid state devices, one example of which is the Triple Level Cell SSD from Samsung. These use 8 voltage levels to represent 8 bits of information per cell (as far as I remember). The details have gotten a little hazy, but this^] article explains it pretty well. In other words, 0 is only represented by the accepted range of the voltage present, as any other value would be.