Computer Architecture : is 0 really 0 ?
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That is not the point. Logical levels are bound to voltages because electrical potential difference is the measured physical quantity. For instance a car battery providing 8A to the vehicle lamps would have no higher logical level than four CR2032 cells providing 20 mA to a red LED (and its series resistor).
THESE PEOPLE REALLY BOTHER ME!! How can they know what you should do without knowing what you want done?!?! -- C++ FQA Lite
I know that, but it doesn't answer the question.
You'll never get very far if all you do is follow instructions.
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Yes, I know that, but it doesn't answer the question.
You'll never get very far if all you do is follow instructions.
Well Voltage 'dropped' across a component, it appears one side, a different value on the other side giving a difference in voltage that can be read with a meter in parallel. Current is the 'thing' (for want of a better word) moving through the circuit to measure it you have to break the path and insert the meter (there are other methods like coils etc. but...). So you can measure a voltage across something with out the being current flow (such as wires before plugging in). Bad explanation but the best I can manage at this time-O-day have a look at howstuffworks.com I seem to remember they had a very basic explanation. I'm off home! :)
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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.
are you really sure?
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are you really sure?
Yes, othrewise I wouldn't ask the question.
You'll never get very far if all you do is follow instructions.
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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.
To answer your exact question: no.
THESE PEOPLE REALLY BOTHER ME!! How can they know what you should do without knowing what you want done?!?! -- C++ FQA Lite
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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.
To answer your exact question: no.
THESE PEOPLE REALLY BOTHER ME!! How can they know what you should do without knowing what you want done?!?! -- C++ FQA Lite
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To answer your exact question: no.
THESE PEOPLE REALLY BOTHER ME!! How can they know what you should do without knowing what you want done?!?! -- C++ FQA Lite
:thumbsup: Exactly.
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 !
Bits can be stored in many many forms . They can be in the polarisation of light , in magnetic state , by the presence or absence of a stored charge . But in electronics the information is usually transmitted as the presence or absence of a voltage . There is usually a very small current associated with that , we don't want a big current . The values of the voltages used and the corresponding currents are somewhat arbitrary . Some systems represent a 1 as the presence of a specific positive voltage ( typically 3 or 5) and some use 0 volts to represent a boolean 0 . This is not mandatory . It is equally possible to represent a 1 as 0 volts and a 0 as (say) 12volts . And if your system is noisy then some systems will use a positive voltage to represent 1 and a negative voltage to represent 0 . There is no hard and fast rule . Although in most systems +5v => 1 and 0v =>0 . There can never be an exact 5v or an exact 0v , you will always have noise induced in the circuit from a wide variety of sources . But the entire reason why binary systems are used is that they are able to handle the noise very well . When the noise voltages are in the millivolt range then it is going to take a lot of noise/bad luck for the noise to be so large that we cannot recognise a 1 and a 0 when using 5v systems . BUT it can and does happen, and it gets worse as the data frequency increases . We do get noise and some technologies are more prone than others . In this case we typicaly add extra bits on the side in order to help . These can be simple parity bits or more complex systems where not only can we detect 1 or 2 bit errors but correct them too. There is nothing stopping you having a system where we use 3 , 4 more voltage levels . And in that way we could have a single line carrying more than one bit of information . But such a system would be more susceptible to noise . In order to reduce the effect of noise you would probably have to slow the data rate . But you do not have to use simple voltage to transmit information you can do all sorts of fancy manipulation of the frequency and phase of a signal , and these are used in broadband . These can have many possible states , but are also less susceptible to noise , enabling the continued growth in the broad band speeds . The whole area is fascinating , if you enjoy electronics. But if you don't enjoy electronics and then its probably easier to think that yes 1 is 5v and 0 is 0v and live in blissful ignorance of what is actually happening several billion times a second in y
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Bits can be stored in many many forms . They can be in the polarisation of light , in magnetic state , by the presence or absence of a stored charge . But in electronics the information is usually transmitted as the presence or absence of a voltage . There is usually a very small current associated with that , we don't want a big current . The values of the voltages used and the corresponding currents are somewhat arbitrary . Some systems represent a 1 as the presence of a specific positive voltage ( typically 3 or 5) and some use 0 volts to represent a boolean 0 . This is not mandatory . It is equally possible to represent a 1 as 0 volts and a 0 as (say) 12volts . And if your system is noisy then some systems will use a positive voltage to represent 1 and a negative voltage to represent 0 . There is no hard and fast rule . Although in most systems +5v => 1 and 0v =>0 . There can never be an exact 5v or an exact 0v , you will always have noise induced in the circuit from a wide variety of sources . But the entire reason why binary systems are used is that they are able to handle the noise very well . When the noise voltages are in the millivolt range then it is going to take a lot of noise/bad luck for the noise to be so large that we cannot recognise a 1 and a 0 when using 5v systems . BUT it can and does happen, and it gets worse as the data frequency increases . We do get noise and some technologies are more prone than others . In this case we typicaly add extra bits on the side in order to help . These can be simple parity bits or more complex systems where not only can we detect 1 or 2 bit errors but correct them too. There is nothing stopping you having a system where we use 3 , 4 more voltage levels . And in that way we could have a single line carrying more than one bit of information . But such a system would be more susceptible to noise . In order to reduce the effect of noise you would probably have to slow the data rate . But you do not have to use simple voltage to transmit information you can do all sorts of fancy manipulation of the frequency and phase of a signal , and these are used in broadband . These can have many possible states , but are also less susceptible to noise , enabling the continued growth in the broad band speeds . The whole area is fascinating , if you enjoy electronics. But if you don't enjoy electronics and then its probably easier to think that yes 1 is 5v and 0 is 0v and live in blissful ignorance of what is actually happening several billion times a second in y
Quote:
The whole area is fascinating , if you enjoy electronics. But if you don't enjoy electronics and then its probably easier to think that yes 1 is 5v and 0 is 0v and live in blissful ignorance of what is actually happening several billion times a second in your humble pc or phone.
Good explanation, I have a feeling that will not be the end though! It fried my brain to think of a one as -5v and a 0 as +5v when I started many moons ago!
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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. :)