Why are computer power supplies like this?

I noticed this before and again last night. I am changing plugs from a
bad supply to a good one. There is a connector with 20 or so wires
that plugs into the motherboard. 6 different color wires. But all the
wire of a poarticular color go to the same trace on the power supply
circuit board. So all the reds to one trace, all the yellows to
another trace and so on. So why all the different wires to the
motherboard? It can't be just because it is harderfigure out how to
route the traces. A bigger connector with more wires costs more money
and every computer I've seen is the same.
Thanks,
Eric

 

[Jim Thompson]

On Fri, 03 Nov 2017 09:20:05 -0700, etpm@whidbey.com wrote:

I noticed this before and again last night. I am changing plugs from a
bad supply to a good one. There is a connector with 20 or so wires
that plugs into the motherboard. 6 different color wires. But all the
wire of a poarticular color go to the same trace on the power supply
circuit board. So all the reds to one trace, all the yellows to
another trace and so on. So why all the different wires to the
motherboard? It can't be just because it is harderfigure out how to
route the traces. A bigger connector with more wires costs more money
and every computer I've seen is the same.
Thanks,
Eric

Current capacity, yet flexibility?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

It's what you learn, after you know it all, that counts.

 

[rickman]

etpm@whidbey.com wrote on 11/3/2017 12:20 PM:

I noticed this before and again last night. I am changing plugs from a
bad supply to a good one. There is a connector with 20 or so wires
that plugs into the motherboard. 6 different color wires. But all the
wire of a poarticular color go to the same trace on the power supply
circuit board. So all the reds to one trace, all the yellows to
another trace and so on. So why all the different wires to the
motherboard? It can't be just because it is harderfigure out how to
route the traces. A bigger connector with more wires costs more money
and every computer I've seen is the same.

Computers use a lot of power. The voltages are low, so the currents are
high. A high end CPU alone can burn 100 watts. That is over 8 amps of
current at 12 volts. To carry that current the connector contacts would
need to be large. So they use multiple contacts and so multiple wires.
This also provides redundancy so if one contact is poor with a high
resistance the others can still carry the current.

The standard for this connector has evolved over the years and there is a
degree of back compatibility with lower power machines. Isn't the connector
actually two connectors, the smaller one optional? Or did they update the
standard again? Or am I just not remembering it correctly?

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

 

On Fri, 3 Nov 2017 13:33:13 -0400, rickman <gnuarm@gmail.com> wrote:

etpm@whidbey.com wrote on 11/3/2017 12:20 PM:
I noticed this before and again last night. I am changing plugs from a
bad supply to a good one. There is a connector with 20 or so wires
that plugs into the motherboard. 6 different color wires. But all the
wire of a poarticular color go to the same trace on the power supply
circuit board. So all the reds to one trace, all the yellows to
another trace and so on. So why all the different wires to the
motherboard? It can't be just because it is harderfigure out how to
route the traces. A bigger connector with more wires costs more money
and every computer I've seen is the same.

Computers use a lot of power. The voltages are low, so the currents are
high. A high end CPU alone can burn 100 watts. That is over 8 amps of
current at 12 volts. To carry that current the connector contacts would
need to be large. So they use multiple contacts and so multiple wires.
This also provides redundancy so if one contact is poor with a high
resistance the others can still carry the current.

The standard for this connector has evolved over the years and there is a
degree of back compatibility with lower power machines. Isn't the connector
actually two connectors, the smaller one optional? Or did they update the
standard again? Or am I just not remembering it correctly?

The last few machines I have worked on have only 1 big connector going
to the motherboard. I don't remember what the older machines were
like. You're explanation makes sense. Thanks.
Eric

 

Compatible replacements have two plugs, and they interlock together.

 

[Ian Field]

<etpm@whidbey.com> wrote in message
news:gulpvct6f7a9nruh2icmd3nv9vo77kj1bu@4ax.com...

On Fri, 3 Nov 2017 13:33:13 -0400, rickman <gnuarm@gmail.com> wrote:

etpm@whidbey.com wrote on 11/3/2017 12:20 PM:
I noticed this before and again last night. I am changing plugs from a
bad supply to a good one. There is a connector with 20 or so wires
that plugs into the motherboard. 6 different color wires. But all the
wire of a poarticular color go to the same trace on the power supply
circuit board. So all the reds to one trace, all the yellows to
another trace and so on. So why all the different wires to the
motherboard? It can't be just because it is harderfigure out how to
route the traces. A bigger connector with more wires costs more money
and every computer I've seen is the same.

Computers use a lot of power. The voltages are low, so the currents are
high. A high end CPU alone can burn 100 watts. That is over 8 amps of
current at 12 volts. To carry that current the connector contacts would
need to be large. So they use multiple contacts and so multiple wires.
This also provides redundancy so if one contact is poor with a high
resistance the others can still carry the current.

The standard for this connector has evolved over the years and there is a
degree of back compatibility with lower power machines. Isn't the
connector
actually two connectors, the smaller one optional? Or did they update the
standard again? Or am I just not remembering it correctly?
The last few machines I have worked on have only 1 big connector going
to the motherboard. I don't remember what the older machines were
like. You're explanation makes sense. Thanks.

Someone recently gave me a HP PSU - its more or less the same form factor as
an ATX PSU, but it has just 2 high current 12V outputs and a few other
wires.

 

[rickman]

Ian Field wrote on 11/6/2017 3:16 PM:

etpm@whidbey.com> wrote in message
news:gulpvct6f7a9nruh2icmd3nv9vo77kj1bu@4ax.com...
On Fri, 3 Nov 2017 13:33:13 -0400, rickman <gnuarm@gmail.com> wrote:

etpm@whidbey.com wrote on 11/3/2017 12:20 PM:
I noticed this before and again last night. I am changing plugs from a
bad supply to a good one. There is a connector with 20 or so wires
that plugs into the motherboard. 6 different color wires. But all the
wire of a poarticular color go to the same trace on the power supply
circuit board. So all the reds to one trace, all the yellows to
another trace and so on. So why all the different wires to the
motherboard? It can't be just because it is harderfigure out how to
route the traces. A bigger connector with more wires costs more money
and every computer I've seen is the same.

Computers use a lot of power. The voltages are low, so the currents are
high. A high end CPU alone can burn 100 watts. That is over 8 amps of
current at 12 volts. To carry that current the connector contacts would
need to be large. So they use multiple contacts and so multiple wires.
This also provides redundancy so if one contact is poor with a high
resistance the others can still carry the current.

The standard for this connector has evolved over the years and there is a
degree of back compatibility with lower power machines. Isn't the connector
actually two connectors, the smaller one optional? Or did they update the
standard again? Or am I just not remembering it correctly?
The last few machines I have worked on have only 1 big connector going
to the motherboard. I don't remember what the older machines were
like. You're explanation makes sense. Thanks.

Someone recently gave me a HP PSU - its more or less the same form factor as
an ATX PSU, but it has just 2 high current 12V outputs and a few other wires.

Does it have special contacts for the 12 volt power connections? Typical
pins are only 1 or 2 amps. So for a 100 watt draw it would need at least 4.
To get more like 4 amps per pin would require contacts with a higher
current rating and so likely larger, perhaps blades rather than round pin
and sockets.

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

 

[Michael A Terrell]

Ian Field wrote:

Someone recently gave me a HP PSU - its more or less the same form
factor as an ATX PSU, but it has just 2 high current 12V outputs and a
few other wires.

I that a computer supply, or is it for some HP test equipment.

 

[Jasen Betts]

On 2017-11-07, rickman <gnuarm@gmail.com> wrote:

Ian Field wrote on 11/6/2017 3:16 PM:

Does it have special contacts for the 12 volt power connections? Typical
pins are only 1 or 2 amps. So for a 100 watt draw it would need at least 4.
To get more like 4 amps per pin would require contacts with a higher
current rating and so likely larger, perhaps blades rather than round pin
and sockets.

Molex claims 6.5A per contact for the nano-fit connectors used to connect
power to PC motherboards

For the CPU there's a separate cable with 4 or 8 contacts half are
ground the other half 12V

--
This email has not been checked by half-arsed antivirus software

 

[Jasen Betts]

On 2017-11-07, rickman <gnuarm@gmail.com> wrote:

Ian Field wrote on 11/6/2017 3:16 PM:

Does it have special contacts for the 12 volt power connections? Typical
pins are only 1 or 2 amps. So for a 100 watt draw it would need at least 4.
To get more like 4 amps per pin would require contacts with a higher
current rating and so likely larger, perhaps blades rather than round pin
and sockets.

Molex claims 6A or more per contact for the "Mini-Fit Jr." connectors used to connect
power to PC motherboards

For the CPU there's a separate cable with 4 or 8 contacts half are
ground the other half 12V

--
This email has not been checked by half-arsed antivirus software

 

[Ian Field]

"Michael A Terrell" <mike.terrell@earthlink.net> wrote in message
news:XbJMB.6$ni6.2@fx19.iad...

Ian Field wrote:

Someone recently gave me a HP PSU - its more or less the same form
factor as an ATX PSU, but it has just 2 high current 12V outputs and a
few other wires.


I that a computer supply, or is it for some HP test equipment.

Maybe some obscure test instrument uses an ATX form factor PSU, that never
occurred to me.

 

et...@whidbey.com wrote:

I noticed this before and again last night. I am changing plugs from a
bad supply to a good one. There is a connector with 20 or so wires
that plugs into the motherboard. 6 different color wires. But all the
wire of a poarticular color go to the same trace on the power supply
circuit board. So all the reds to one trace, all the yellows to
another trace and so on. So why all the different wires to the
motherboard? It can't be just because it is harderfigure out how to
route the traces.

The company does want to encourage you to buy a new one.

A bigger connector with more wires costs more money
and every computer I've seen is the same.

Parts are cheaper, smaller and more difficult for non manufacturing or service people to replace every day.

 

[Michael A Terrell]

Ian Field wrote:

"Michael A Terrell" <mike.terrell@earthlink.net> wrote in message
news:XbJMB.6$ni6.2@fx19.iad...
Ian Field wrote:

Someone recently gave me a HP PSU - its more or less the same form
factor as an ATX PSU, but it has just 2 high current 12V outputs and a
few other wires.


Is that a computer supply, or is it for some HP test equipment.

Maybe some obscure test instrument uses an ATX form factor PSU, that
never occurred to me.

Apparently, HP/Agilent uses them. I see question on the HP/Agilent
Yahoo group about failed SMPS with them.