 |
|
|
|
Next: Recovery Disk
|
| Author |
Message |
External
Since: Jun 21, 2004
Posts: 33
|
(Msg. 1) Posted: Sun Oct 29, 2006 5:07 pm
Post subject: Power Supply Oddity
Archived from groups: microsoft>public>windowsxp>hardware (more info?)
|
|
|
I just noticed after a long, long time that the PC Health BIOS display for
my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
just fine so I decided to look into it a little bit. I discovered the power
connector on supply does not have a wire on pin 18 ( that is where the MB
manual says it expects -5v) so of course the BIOS was reporting 0v.
No one around here knows what the -5v might have been used for nor why the
manual calls for it on pin 18 when the it apparently lives happily without
it. I remember that back in TTL days, -5v was commonly used.
Can someone clue me in here?
Thank you |
|
| Back to top |
|
 | |
External
Since: Mar 08, 2005
Posts: 1
|
(Msg. 2) Posted: Sun Oct 29, 2006 10:02 pm
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
Jack Gillis wrote:
> I just noticed after a long, long time that the PC Health BIOS display for
> my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
> just fine so I decided to look into it a little bit. I discovered the power
> connector on supply does not have a wire on pin 18 ( that is where the MB
> manual says it expects -5v) so of course the BIOS was reporting 0v.
>
> No one around here knows what the -5v might have been used for nor why the
> manual calls for it on pin 18 when the it apparently lives happily without
> it. I remember that back in TTL days, -5v was commonly used.
>
> Can someone clue me in here?
>
> Thank you
Quoted from Upgrading and Repairing PCs by Scott Mueller, 15th Edition
Ch.21
"If you look at a specification sheet for a typical PC power supply, you
can see that the supply generates not only +3.3V, +5V, and +12V, but
also –5V and –12V. The positive voltages seemingly power everything in
the system (logic and motors), so what are the negative voltages used
for? The answer is not much! Some of the power supply designs, such as
the small form factor (SFX) design, no longer include the –5V output for
that reason. The only reason it has remained in most power supply
designs is that –5V is required on the Industry Standard Architecture
(ISA) bus for full backward-compatibility.
Although –5V and –12V are supplied to the motherboard via the power
supply connectors, the motherboard normally uses only the +3.3V, +5V,
and +12V. The –5V is simply routed to the ISA bus on pin B5 so any ISA
cards can use it, even though not many do today. However, as an example,
the analog data separator circuits found in older floppy controllers do
use –5V.
The motherboard logic typically doesn't use –12V either; however, it
might be used in some board designs for serial port or LAN circuits." |
|
| Back to top |
|
| |
External
Since: Jun 21, 2004
Posts: 33
|
(Msg. 3) Posted: Mon Oct 30, 2006 5:51 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
"John Coode" <faecius DeleteThis @yahoo.co.uk> wrote in message
news:uldkvb8%23GHA.4712@TK2MSFTNGP03.phx.gbl...
> Jack Gillis wrote:
>> I just noticed after a long, long time that the PC Health BIOS display
>> for my Biostar M7VIG motherboard reports 0v for the -5v rail. The system
>> works just fine so I decided to look into it a little bit. I discovered
>> the power connector on supply does not have a wire on pin 18 ( that is
>> where the MB manual says it expects -5v) so of course the BIOS was
>> reporting 0v.
>>
>> No one around here knows what the -5v might have been used for nor why
>> the manual calls for it on pin 18 when the it apparently lives happily
>> without it. I remember that back in TTL days, -5v was commonly used.
>>
>> Can someone clue me in here?
>>
>> Thank you
>
>
> Quoted from Upgrading and Repairing PCs by Scott Mueller, 15th Edition
> Ch.21
>
> "If you look at a specification sheet for a typical PC power supply, you
> can see that the supply generates not only +3.3V, +5V, and +12V, but
> also –5V and –12V. The positive voltages seemingly power everything in the
> system (logic and motors), so what are the negative voltages used for? The
> answer is not much! Some of the power supply designs, such as the small
> form factor (SFX) design, no longer include the –5V output for that
> reason. The only reason it has remained in most power supply designs is
> that –5V is required on the Industry Standard Architecture (ISA) bus for
> full backward-compatibility.
>
> Although –5V and –12V are supplied to the motherboard via the power supply
> connectors, the motherboard normally uses only the +3.3V, +5V, and +12V.
> The –5V is simply routed to the ISA bus on pin B5 so any ISA cards can use
> it, even though not many do today. However, as an example, the analog data
> separator circuits found in older floppy controllers do use –5V.
>
> The motherboard logic typically doesn't use –12V either; however, it might
> be used in some board designs for serial port or LAN circuits."
>
Thank you John for the extensive answer. That could explain why when I put
the machine together I found one of my PCI cards wouldn't work. No big
deal.
Thanks again. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Aug 19, 2005
Posts: 16
|
(Msg. 4) Posted: Mon Oct 30, 2006 5:55 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
-5 volts had a number of functions. Originally, processors such as
8080 and other chips required -5 V so that transistors on the substate
(inside chip) were electrically isolated. That - voltage is now
created inside on chips.
A second function involves op amps - analog type circuits that need
both +5 and -5 volts. However that -5 volts can also be created from
the -12 volts.
Some peripheral interfaces also required a + and - voltage. But
again, newer chips create that - voltage from the + voltage. IOW -5
and -12 volts remain mostly for legacy reasons.
TTL, CMOS, and other digital families providing same logic functions
don't use -5 volts. However other (rare) technologies such as ECL did
use - voltages.
Missing -5 volts would cause no problems to any PCI card since PCI
bus does not have -5 volt pins.
Purpose of -5 V would be obvious to those with hardware experience.
Its function makes an excellent benchmark to discover those who
actually have basic electronics knowledge.
Jack Gillis wrote:
> I just noticed after a long, long time that the PC Health BIOS display for
> my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
> just fine so I decided to look into it a little bit. I discovered the power
> connector on supply does not have a wire on pin 18 ( that is where the MB
> manual says it expects -5v) so of course the BIOS was reporting 0v.
>
> No one around here knows what the -5v might have been used for nor why the
> manual calls for it on pin 18 when the it apparently lives happily without
> it. I remember that back in TTL days, -5v was commonly used.
>
> Can someone clue me in here? >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 5) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX.RemoveThis@widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 6) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX DeleteThis @widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 7) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX.RemoveThis@widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 8) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX.DeleteThis@widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 9) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX DeleteThis @widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 10) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX.TakeThisOut@widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 11) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX.DeleteThis@widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 12) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX RemoveThis @widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 13) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX.TakeThisOut@widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 14) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX.RemoveThis@widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
External
Since: Apr 28, 2006
Posts: 90
|
(Msg. 15) Posted: Sat Nov 04, 2006 8:49 am
Post subject: Re: Power Supply Oddity [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
|
|
|
On Sun, 29 Oct 2006 17:07:45 -0500, "Jack Gillis"
<XXXXXXXX.TakeThisOut@widomaker.com> wrote:
>I just noticed after a long, long time that the PC Health BIOS display for
>my Biostar M7VIG motherboard reports 0v for the -5v rail. The system works
>just fine so I decided to look into it a little bit. I discovered the power
>connector on supply does not have a wire on pin 18 ( that is where the MB
>manual says it expects -5v) so of course the BIOS was reporting 0v.
>
>No one around here knows what the -5v might have been used for nor why the
>manual calls for it on pin 18 when the it apparently lives happily without
>it. I remember that back in TTL days, -5v was commonly used.
>
>Can someone clue me in here?
In addition to the other comments I've had an encounter with a power
supply that didn't put out -5V and the board itself wouldn't consider
booting. >> Stay informed about: Power Supply Oddity |
|
| Back to top |
|
| |
|
You can post new topics in this forum
You can reply to topics in this forum
You can edit your posts in this forum
You can delete your posts in this forum
You can vote in polls in this forum
|
|
|
|
|
|
|
FAQ
Profile
Private Messages
Log in
