what is the purpose of -ve voltage in PC?

Hi,
I want to know what is the purpose of -ve voltages in PC ? for example -5v, -
3.3v, -12v. It knows to a common man that +ve voltages flows current and i
would like to know the purpose of -ve voltages.

Also can you get me some links for easy understanding for power consumption
of a PC and SERVERS which can be in easily understandable manner?. In general
we identifying power consumption by adding all the power consumption of
peripherals like keyboard, motherboard, PCI devices etc., But May i know what
power consumes generally PIII, PIV PCs consumes per hour ?

Thanks in advance
chandra

--
chandra

Message posted via HWKB.com
http://www.hwkb.com/Uwe/Forums.aspx/...-asus/200705/1

Do a search for power supply calculators, and you will find the information
there.

There are a few around.

With CPUs and VGA cards they will usually state the maximum power
consumption.

Adding up all of your peripherals will result in an over estimation, as
generally that would mean all of your peripherals are running at full load
all of the time, which isn't the case normally.


"gchandrujs via HWKB.com" <u25485@uwe> wrote in message
news:72a4666beb021@uwe...
> Hi,
> I want to know what is the purpose of -ve voltages in PC ? for
> example -5v, -
> 3.3v, -12v. It knows to a common man that +ve voltages flows current and i
> would like to know the purpose of -ve voltages.
>
> Also can you get me some links for easy understanding for power
> consumption
> of a PC and SERVERS which can be in easily understandable manner?. In
> general
> we identifying power consumption by adding all the power consumption of
> peripherals like keyboard, motherboard, PCI devices etc., But May i know
> what
> power consumes generally PIII, PIV PCs consumes per hour ?
>
> Thanks in advance
> chandra
>
> --
> chandra
>
> Message posted via HWKB.com
> http://www.hwkb.com/Uwe/Forums.aspx/...-asus/200705/1
>

gchandrujs via HWKB.com wrote:
> Hi,
> I want to know what is the purpose of -ve voltages in PC ? for example -5v, -
> 3.3v, -12v. It knows to a common man that +ve voltages flows current and i
> would like to know the purpose of -ve voltages.
>
> Also can you get me some links for easy understanding for power consumption
> of a PC and SERVERS which can be in easily understandable manner?. In general
> we identifying power consumption by adding all the power consumption of
> peripherals like keyboard, motherboard, PCI devices etc., But May i know what
> power consumes generally PIII, PIV PCs consumes per hour ?
>
> Thanks in advance
> chandra
>

In my computer, the -12V is used by the RS-232 interface chip for the
serial port. They stopped using -5V years ago, but there are occasionally
motherboards that still use it. -5V has been removed from pin 18, on
the last couple of ATX power supply specifications.

There are several sites which offer to compute the power consumption
of a computer, based on the components used. But I haven't seen one
of those web sites yet, that does a good job. I used to like the
Takaman.jp site (because of its spreadsheet output format), but the
site is closed. The other sites tend to overestimate the power.

The Takaman site was archived here, but I'm not sure this is working
correctly right now. Anyway, this seems to work in Firefox OK. You
can select the line items, and get some idea of their contribution.

http://web.archive.org/web/200404110...c.html?english

Anandtech offers some total power numbers here. So
the "average" 3GHz P4 computer is 122W idle and 195W busy.

http://www.anandtech.com/showdoc.aspx?i=2275&p=13

Paul

"gchandrujs via HWKB.com" <u25485@uwe> wrote in message
news:72a4666beb021@uwe...
> Hi,
> I want to know what is the purpose of -ve voltages in PC ? for
> example -5v, -
> 3.3v, -12v. It knows to a common man that +ve voltages flows current and
> i
> would like to know the purpose of -ve voltages.
Think of the 'flow', like a water circuit. Water can be pumped round the
circuit in either direction, but there always has to be a complete
'circuit'. In fact the actual electron 'flow' in a circuit, is the
opposite way to the 'sign', so it is the -ve connection, that 'sources'
electrons, and the +ve ones, have the electrons flowing towards them!.
With the positive connections, electrons are flowing 'out' from the 0v
wire, through the circuit, and back into the +ve connection. With the
negative connections, the electrons are flowing out of these connections,
through the circuit, and back into the 0v pin. It is one of the oddities
of history, that we have the flow 'backwards', from what would seem
intuitive...
Now, just as with the water analogy, there can be places where water needs
pumping 'up' (cistern in the roof for example), and others where flow in
the other direction is needed. Most modern stuff, doesn't really use
the -ve rails now. Instead if -ve lines are needed, the circuits will
contain their own 'charge pump', to provide these rails, drawing the
required power fom the +ve rails, and moving this where needed (the
circuit used, works just like a 'bucket brigade' of firemen). However in
the past, this was much harder to do, and so -ve rails were provided. The
basic uses were:
The -5v rail, was required by the original memories on the PC. Modern
memories generate their own internal rail.
The -12v rail, was used by the RS232 signalling standard (to improve noise
immunity, quite a large signalling voltage is used on this, -12v to +12v
normally at the 'source').
This rail was also commonly used by audio circuits, which want their
output voltages to have 'symmetrical' swings around the 0v rail.
There isn't a -3.3v rail in the AT.

> Also can you get me some links for easy understanding for power
> consumption
> of a PC and SERVERS which can be in easily understandable manner?. In
> general
> we identifying power consumption by adding all the power consumption of
> peripherals like keyboard, motherboard, PCI devices etc., But May i know
> what
> power consumes generally PIII, PIV PCs consumes per hour ?
>
> Thanks in advance
Varies massively. The processor itself, depending on speed, and what is
actually being done, can draw anything from about 10W, to nearly 200W.
Most current units are specified to dissipate about 90W max). The second
biggest user, is the video card, with some of the modern high performance
cards having 'peak' demands well over 100W. Systems using two such cards
in SLI, or a similar manner, can have huge demands in this area. However
quite competent basic displays can be done using well under 10W, and
typically cards like this will be used in server applications. Disk
drives, use between about 2W (some low power designs), up to nearly 30W
(15000RPM server drive). CD drives generally use about 10W. Memory, about
5W/GB (depends on the speed as well). Keyboards/mice etc., will all use
under 5W (remember this is the maximum a USB device can draw without
external power, and hence provides a good 'guideline').

Best Wishes

Paul wrote:
>> Hi,
>> I want to know what is the purpose of -ve voltages in PC ? for example -5v, -
>[quoted text clipped - 9 lines]
>> Thanks in advance
>> chandra
>
>In my computer, the -12V is used by the RS-232 interface chip for the
>serial port. They stopped using -5V years ago, but there are occasionally
>motherboards that still use it. -5V has been removed from pin 18, on
>the last couple of ATX power supply specifications.
>
>There are several sites which offer to compute the power consumption
>of a computer, based on the components used. But I haven't seen one
>of those web sites yet, that does a good job. I used to like the
>Takaman.jp site (because of its spreadsheet output format), but the
>site is closed. The other sites tend to overestimate the power.
>
>The Takaman site was archived here, but I'm not sure this is working
>correctly right now. Anyway, this seems to work in Firefox OK. You
>can select the line items, and get some idea of their contribution.
>
>http://web.archive.org/web/200404110...c.html?english
>
>Anandtech offers some total power numbers here. So
>the "average" 3GHz P4 computer is 122W idle and 195W busy.
>
>http://www.anandtech.com/showdoc.aspx?i=2275&p=13
>
> Paul

Thank you all for your replies. Much easy to understand that a PIV pc
consumes nearly 195W during busy load.

However regarding -ve voltages, i mean to ask in the concept of electronics
that what is negative voltage. Generally even a common man understands that
positive voltages means, the electron flow will be there and the power comes.
But what it mean the -ve voltage and what does it do ?

Thanks in advance and awaiting to get back from you all.

Regards
Chandra

--
chandra

Message posted via http://www.hwkb.com

Negative voltages are just voltages where positive and negative are
reversed so that the electricity flows in the "other" direction.

Negative voltages are not used much any more, but one on a time were
common (RS-232 serial ports still use them, but once they were used by
other devices as well; for example, some old CPU chips and memory chips
required them).


gchandrujs via HWKB.com wrote:
> Paul wrote:
>>> Hi,
>>> I want to know what is the purpose of -ve voltages in PC ? for example -5v, -
>> [quoted text clipped - 9 lines]
>>> Thanks in advance
>>> chandra
>> In my computer, the -12V is used by the RS-232 interface chip for the
>> serial port. They stopped using -5V years ago, but there are occasionally
>> motherboards that still use it. -5V has been removed from pin 18, on
>> the last couple of ATX power supply specifications.
>>
>> There are several sites which offer to compute the power consumption
>> of a computer, based on the components used. But I haven't seen one
>> of those web sites yet, that does a good job. I used to like the
>> Takaman.jp site (because of its spreadsheet output format), but the
>> site is closed. The other sites tend to overestimate the power.
>>
>> The Takaman site was archived here, but I'm not sure this is working
>> correctly right now. Anyway, this seems to work in Firefox OK. You
>> can select the line items, and get some idea of their contribution.
>>
>> http://web.archive.org/web/200404110...c.html?english
>>
>> Anandtech offers some total power numbers here. So
>> the "average" 3GHz P4 computer is 122W idle and 195W busy.
>>
>> http://www.anandtech.com/showdoc.aspx?i=2275&p=13
>>
>> Paul
>
> Thank you all for your replies. Much easy to understand that a PIV pc
> consumes nearly 195W during busy load.
>
> However regarding -ve voltages, i mean to ask in the concept of electronics
> that what is negative voltage. Generally even a common man understands that
> positive voltages means, the electron flow will be there and the power comes.
> But what it mean the -ve voltage and what does it do ?
>
> Thanks in advance and awaiting to get back from you all.
>
> Regards
> Chandra
>

Dear Barry,

Thanks for your reply. So, i understand the negative voltages are just the
flow in opposite direction. Hope i am on right think. How can we mean to say
only particular direction the electricity flow which we say +ve voltages ?

If so, Serial ports are using -ve voltages, which mean the electricity flows
back from serial port to main supply or motherboard ? Whats the use in that ?

Please explain.

THanks in advance
chandra


Barry Watzman wrote:
>Negative voltages are just voltages where positive and negative are
>reversed so that the electricity flows in the "other" direction.
>
>Negative voltages are not used much any more, but one on a time were
>common (RS-232 serial ports still use them, but once they were used by
>other devices as well; for example, some old CPU chips and memory chips
>required them).
>
>>>> Hi,
>>>> I want to know what is the purpose of -ve voltages in PC ? for example -5v, -
>[quoted text clipped - 37 lines]
>> Regards
>> Chandra

--
chandra

Message posted via HWKB.com
http://www.hwkb.com/Uwe/Forums.aspx/...-asus/200705/1

"gchandrujs via HWKB.com" <u25485@uwe> wrote in message
news:72b0b9fb7385d@uwe...
> Dear Barry,
>
> Thanks for your reply. So, i understand the negative voltages are just
> the
> flow in opposite direction. Hope i am on right think. How can we mean to
> say
> only particular direction the electricity flow which we say +ve voltages
> ?
>
> If so, Serial ports are using -ve voltages, which mean the electricity
> flows
> back from serial port to main supply or motherboard ? Whats the use in
> that ?
>
> Please explain.
>
> THanks in advance
> chandra
The flow is always _circular_. It is pumped round by the voltage 'source'.
As I already posted, it is the +ve voltages that have the flow
'backwards'!. The electrons here, flow out along the 0v (GND) wire, and
back in on the +ve wire. With the -ve voltages, the electrons flow out
along the -ve wire, and back in on the 0v wire.

Best Wishes

> Barry Watzman wrote:
>>Negative voltages are just voltages where positive and negative are
>>reversed so that the electricity flows in the "other" direction.
>>
>>Negative voltages are not used much any more, but one on a time were
>>common (RS-232 serial ports still use them, but once they were used by
>>other devices as well; for example, some old CPU chips and memory chips
>>required them).
>>
>>>>> Hi,
>>>>> I want to know what is the purpose of -ve voltages in PC ? for
>>>>> example -5v, -
>>[quoted text clipped - 37 lines]
>>> Regards
>>> Chandra
>
> --
> chandra
>
> Message posted via HWKB.com
> http://www.hwkb.com/Uwe/Forums.aspx/...-asus/200705/1
>

"gchandrujs via HWKB.com" <u25485@uwe> wrote in message
news:72a4666beb021@uwe...
> Hi,
> I want to know what is the purpose of -ve voltages in PC ? for
> example -5v, -
> 3.3v, -12v. It knows to a common man that +ve voltages flows current and i
> would like to know the purpose of -ve voltages.
>
> Also can you get me some links for easy understanding for power
> consumption
> of a PC and SERVERS which can be in easily understandable manner?. In
> general
> we identifying power consumption by adding all the power consumption of
> peripherals like keyboard, motherboard, PCI devices etc., But May i know
> what
> power consumes generally PIII, PIV PCs consumes per hour ?
>
> Thanks in advance
> chandra
>
> --
> chandra
>
> Message posted via HWKB.com
> http://www.hwkb.com/Uwe/Forums.aspx/...-asus/200705/1
>

This is going to date me.

Us electronic guys used to use large voltages to get things done. Lots of
voltage, so things didn't get lost in the works. Tube stuff often used +-
400 volts, and transistor circuits used +-5v, and signal paths used +-12v
all the time. You had to, to get the signal from one place to another.
Those serial terminals might be 200 or more feet away from the computer
room, and those lines might be run alongside of who knows what. Those other
cables messing things up with their own noise. So the larger the signal,
the better. Made it easier to detect the signal on the receiving end.

Time marched on, and noise cancellation got better, signal detection got
easier, and noise levels dropped. Their was a certain "cemetery" to +-
voltages. That is, voltage above "ground" and voltage below "ground"
Ground being the potential of the dirt you were standing on, or the pole
sticking out of the ground you hooked your trusty multi-meter to to measure
whatever you wanted too.

You could just as easily used 0 to +24v for serial cables and call +12v
ground, (without having reference to "earth" ground). As I said, time
marched on, and the need for BIG signals was lost in small distance signal
distribution. Electronics got smaller, used less current, (per component)
and needed lower and lower voltages to operate. Electronics went from tubes
to transistors to complementary metal oxide semiconductors, (CMOS). CMOS
could run on anything from ~+-19 volts to ~+-3 volts when first introduced.
(I made lots of stuff out of the CD4000 series, the good old days now.)

Well, time marches on, and voltage is bad. It causes heat, and other bad
things to happen. (By the way, thermal expansion and contraction is the
number one cause of component failure in electronics!) So manufacturers go
out of their way to reduce voltage requirements of their IC's, be they CPU,
RAM, Controllers, Routers, or whatever. Usually you will see higher
voltages used around I/0 (Input /Output) circuits, but that will change too.
Lower voltages let us use smaller components for manufacturing too.

So you don't see much call for negative voltages, though that is relative,
and you don't see much need for any "relatively" large voltages in computers
anymore either. Computer manufacturers could stop using +12 volts if they
wanted to, but they would have to double the current ratings if they did,
W=VxI (watts equals volts times current). So if you half the voltage, you
double the current required to do the same job.

I could go on.

William

"Roger Hamlett" <> wrote in message
newsve5i.3420$...


> In fact the actual electron 'flow' in a circuit, is the opposite way to
> the 'sign', so it is the -ve connection, that 'sources' electrons, and the
> +ve ones, have the electrons flowing towards them!.

Good description Roger.

I always showed my schematics having the flow from positive to negative.
Few could call me out on this. And when they did, I would say "You can't
move an electron without a hole existing first" Which would shut them all
up. No one could disk me on that bs.

Thanks for the memories.

William